diff --git a/src/app/[locale]/layout.tsx b/src/app/[locale]/layout.tsx
index b2d14bc..bc1188c 100644
--- a/src/app/[locale]/layout.tsx
+++ b/src/app/[locale]/layout.tsx
@@ -2,19 +2,14 @@ import { notFound } from 'next/navigation';
 import { NextIntlClientProvider } from 'next-intl';
 import { getMessages, setRequestLocale } from 'next-intl/server';
 import { Inter } from 'next/font/google';
-import dynamic from 'next/dynamic';
 import { locales, localeMetadata, seoKeywords, type Locale } from '@/i18n/config';
 import type { Metadata } from 'next';
 import { Header, Footer, GlobalBackground } from '@/components/layout';
 import { PersonJsonLd, ProfessionalServiceJsonLd, OrganizationJsonLd, WebSiteJsonLd } from '@/components/seo';
 import { WebVitals } from '@/components/analytics';
+import { ChatbotLoader } from '@/components/chat/ChatbotLoader';
 import '../globals.css';
 
-// Lazy load Chatbot component - uses browser-only APIs (localStorage)
-const Chatbot = dynamic(() => import('@/components/chat/Chatbot').then((mod) => mod.Chatbot), {
-  ssr: false,
-});
-
 const inter = Inter({
   subsets: ['latin'],
   display: 'swap',
@@ -130,7 +125,7 @@ export default async function LocaleLayout({ children, params }: Props) {
             <Footer />
           </div>
           {/* AI Chatbot - lazy loaded for performance */}
-          <Chatbot />
+          <ChatbotLoader />
         </NextIntlClientProvider>
         {/* Core Web Vitals monitoring */}
         <WebVitals />
diff --git a/src/components/chat/ChatbotLoader.tsx b/src/components/chat/ChatbotLoader.tsx
new file mode 100644
index 0000000..78e6e69
--- /dev/null
+++ b/src/components/chat/ChatbotLoader.tsx
@@ -0,0 +1,17 @@
+'use client';
+
+import dynamic from 'next/dynamic';
+
+/**
+ * Client-side wrapper for the Chatbot component.
+ * Uses dynamic import with ssr: false to prevent hydration issues
+ * with browser-only APIs like localStorage.
+ */
+const Chatbot = dynamic(
+  () => import('./Chatbot').then((mod) => mod.Chatbot),
+  { ssr: false }
+);
+
+export function ChatbotLoader() {
+  return <Chatbot />;
+}
diff --git a/src/components/chat/index.ts b/src/components/chat/index.ts
index a84dddb..a8986af 100644
--- a/src/components/chat/index.ts
+++ b/src/components/chat/index.ts
@@ -3,5 +3,6 @@
  */
 
 export { Chatbot } from './Chatbot';
+export { ChatbotLoader } from './ChatbotLoader';
 export { ChatMessage, TypingIndicator, WelcomeMessage } from './ChatMessage';
 export type { ChatMessageData, ChatRole } from './ChatMessage';
diff --git a/tests/e2e/functionality.spec.ts b/tests/e2e/functionality.spec.ts
new file mode 100644
index 0000000..c8b3b5e
--- /dev/null
+++ b/tests/e2e/functionality.spec.ts
@@ -0,0 +1,611 @@
+import { test, expect } from '@playwright/test';
+
+/**
+ * Functionality Test Suite
+ *
+ * This suite tests core site functionality including:
+ * - Navigation (desktop and mobile)
+ * - Contact form validation and submission
+ * - Language switching between all locales (de, en, sr)
+ *
+ * These tests verify user flows work correctly across the application.
+ */
+
+// Locales to test
+const LOCALES = ['de', 'en', 'sr'] as const;
+
+// Navigation pages configuration
+const NAVIGATION_PAGES = [
+  { path: '', name: 'Home', navKey: 'home' },
+  { path: '/about', name: 'About', navKey: 'about' },
+  { path: '/leistungen', name: 'Services', navKey: 'services' },
+  { path: '/portfolio', name: 'Portfolio', navKey: 'portfolio' },
+  { path: '/blog', name: 'Blog', navKey: 'blog' },
+  { path: '/contact', name: 'Contact', navKey: 'contact' },
+] as const;
+
+/**
+ * Navigation Tests
+ *
+ * Verify that all navigation links work correctly and pages load without errors.
+ */
+test.describe('Navigation', () => {
+  test.describe('Page Loading', () => {
+    for (const pageConfig of NAVIGATION_PAGES) {
+      test(`${pageConfig.name} page loads successfully (de)`, async ({ page }) => {
+        const url = `/de${pageConfig.path}`;
+        const response = await page.goto(url, {
+          waitUntil: 'domcontentloaded',
+        });
+
+        // Verify response is successful
+        expect(response?.status()).toBeLessThan(400);
+
+        // Verify page has content
+        const body = page.locator('body');
+        await expect(body).toBeVisible();
+
+        // Verify no JavaScript errors (basic check)
+        const errors: string[] = [];
+        page.on('pageerror', (error) => {
+          errors.push(error.message);
+        });
+
+        // Wait for page to stabilize
+        await page.waitForLoadState('networkidle');
+
+        // Filter out non-critical errors
+        const criticalErrors = errors.filter(
+          (error) =>
+            !error.includes('analytics') &&
+            !error.includes('gtag') &&
+            !error.includes('ResizeObserver')
+        );
+
+        expect(criticalErrors).toHaveLength(0);
+      });
+    }
+  });
+
+  test.describe('Desktop Navigation Links', () => {
+    test('Header navigation links work correctly', async ({ page }) => {
+      // Start from homepage
+      await page.goto('/de', {
+        waitUntil: 'networkidle',
+      });
+
+      // Verify navigation is visible
+      const nav = page.locator('nav[role="navigation"]');
+      await expect(nav).toBeVisible();
+
+      // Test clicking on About link
+      const aboutLink = page.locator('nav a[href="/de/about"]').first();
+      await expect(aboutLink).toBeVisible();
+      await aboutLink.click();
+
+      // Verify URL changed
+      await expect(page).toHaveURL(/\/de\/about/);
+
+      // Verify About page content loaded
+      await page.waitForLoadState('networkidle');
+    });
+
+    test('Logo link navigates to homepage', async ({ page }) => {
+      // Start from about page
+      await page.goto('/de/about', {
+        waitUntil: 'networkidle',
+      });
+
+      // Click logo
+      const logo = page.locator('nav a[href="/de"]').first();
+      await expect(logo).toBeVisible();
+      await logo.click();
+
+      // Verify navigated to homepage
+      await expect(page).toHaveURL(/\/de\/?$/);
+    });
+
+    test('Active navigation state is applied correctly', async ({ page }) => {
+      // Go to About page
+      await page.goto('/de/about', {
+        waitUntil: 'networkidle',
+      });
+
+      // The active link should have a different background color
+      const aboutLink = page.locator('nav a[href="/de/about"]').first();
+
+      // Check that the link has the active class styling (bg-zinc-700/60)
+      await expect(aboutLink).toHaveClass(/bg-zinc-700/);
+    });
+  });
+
+  test.describe('Mobile Navigation', () => {
+    test.use({ viewport: { width: 375, height: 812 } });
+
+    test('Mobile menu opens and closes', async ({ page }) => {
+      await page.goto('/de', {
+        waitUntil: 'networkidle',
+      });
+
+      // Find mobile menu button
+      const menuButton = page.locator('button[aria-label="Open menu"]');
+      await expect(menuButton).toBeVisible();
+
+      // Open menu
+      await menuButton.click();
+
+      // Verify mobile menu is visible
+      const mobileMenu = page.locator('#mobile-menu');
+      await expect(mobileMenu).toBeVisible();
+
+      // Close menu using close button in sidebar
+      const closeButton = page.locator('#mobile-menu button[aria-label="Close sidebar"]');
+      await expect(closeButton).toBeVisible();
+      await closeButton.click();
+
+      // Verify menu is closed (translated off-screen)
+      await expect(mobileMenu).toHaveClass(/translate-x-full/);
+    });
+
+    test('Mobile menu navigation works', async ({ page }) => {
+      await page.goto('/de', {
+        waitUntil: 'networkidle',
+      });
+
+      // Open mobile menu
+      const menuButton = page.locator('button[aria-label="Open menu"]');
+      await menuButton.click();
+
+      // Wait for menu to be visible
+      const mobileMenu = page.locator('#mobile-menu');
+      await expect(mobileMenu).toBeVisible();
+
+      // Click on About link in mobile menu
+      const aboutLink = mobileMenu.locator('a[href="/de/about"]');
+      await expect(aboutLink).toBeVisible();
+      await aboutLink.click();
+
+      // Verify navigation occurred
+      await expect(page).toHaveURL(/\/de\/about/);
+
+      // Verify menu closed after navigation
+      await page.waitForTimeout(500); // Wait for animation
+      await expect(mobileMenu).toHaveClass(/translate-x-full/);
+    });
+  });
+});
+
+/**
+ * Contact Form Tests
+ *
+ * Verify form validation, error handling, and successful submission.
+ */
+test.describe('Contact Form', () => {
+  test.beforeEach(async ({ page }) => {
+    await page.goto('/de/contact', {
+      waitUntil: 'networkidle',
+    });
+  });
+
+  test('Form renders with all required fields', async ({ page }) => {
+    // Verify form fields exist
+    const nameInput = page.locator('input#name');
+    const emailInput = page.locator('input#email');
+    const messageTextarea = page.locator('textarea#message');
+    const submitButton = page.locator('button[type="submit"]');
+
+    await expect(nameInput).toBeVisible();
+    await expect(emailInput).toBeVisible();
+    await expect(messageTextarea).toBeVisible();
+    await expect(submitButton).toBeVisible();
+  });
+
+  test('Form shows validation errors for empty fields', async ({ page }) => {
+    // Try to submit empty form
+    const submitButton = page.locator('button[type="submit"]');
+    await submitButton.click();
+
+    // Check for validation error messages
+    const errorMessages = page.locator('.text-red-400');
+    await expect(errorMessages.first()).toBeVisible();
+
+    // Should have at least 3 error messages (name, email, message)
+    const errorCount = await errorMessages.count();
+    expect(errorCount).toBeGreaterThanOrEqual(3);
+  });
+
+  test('Form validates email format', async ({ page }) => {
+    // Fill only name and message, leaving email empty initially
+    await page.fill('input#name', 'Test User');
+    await page.fill('textarea#message', 'Test message content');
+
+    // Leave email empty and submit
+    const submitButton = page.locator('button[type="submit"]');
+    await submitButton.click();
+
+    // Should show email validation error (for empty email)
+    const emailError = page.locator('.text-red-400');
+    await expect(emailError.first()).toBeVisible({ timeout: 5000 });
+
+    // Verify it's related to email by checking text contains email-related content
+    // The form should have validation errors visible
+    const errorCount = await emailError.count();
+    expect(errorCount).toBeGreaterThan(0);
+  });
+
+  test('Form clears errors when user starts typing', async ({ page }) => {
+    // Submit empty form to trigger errors
+    const submitButton = page.locator('button[type="submit"]');
+    await submitButton.click();
+
+    // Verify error is shown
+    const errorMessages = page.locator('.text-red-400');
+    await expect(errorMessages.first()).toBeVisible();
+
+    // Start typing in name field
+    const nameInput = page.locator('input#name');
+    await nameInput.fill('Test');
+
+    // Wait for error to clear for name field
+    await page.waitForTimeout(100);
+
+    // The number of errors should be reduced
+    const remainingErrors = await errorMessages.count();
+    expect(remainingErrors).toBeLessThanOrEqual(2);
+  });
+
+  test('Form submits successfully with valid data', async ({ page }) => {
+    // Fill in valid form data
+    await page.fill('input#name', 'Test User');
+    await page.fill('input#email', 'test@example.com');
+    await page.fill('textarea#message', 'This is a test message for the contact form.');
+
+    // Submit form
+    const submitButton = page.locator('button[type="submit"]');
+    await submitButton.click();
+
+    // Wait for loading state
+    const loadingSpinner = page.locator('.animate-spin');
+    await expect(loadingSpinner).toBeVisible();
+
+    // Wait for success message (form has simulated delay)
+    const successMessage = page.locator('.bg-green-900\\/20');
+    await expect(successMessage).toBeVisible({ timeout: 5000 });
+
+    // Verify form fields are cleared
+    const nameInput = page.locator('input#name');
+    await expect(nameInput).toHaveValue('');
+  });
+
+  test('Form fields are disabled during submission', async ({ page }) => {
+    // Fill in valid form data
+    await page.fill('input#name', 'Test User');
+    await page.fill('input#email', 'test@example.com');
+    await page.fill('textarea#message', 'This is a test message.');
+
+    // Submit form
+    const submitButton = page.locator('button[type="submit"]');
+    await submitButton.click();
+
+    // Check that fields are disabled during submission
+    const nameInput = page.locator('input#name');
+    await expect(nameInput).toBeDisabled();
+
+    // Wait for submission to complete
+    await page.waitForTimeout(2000);
+  });
+});
+
+/**
+ * Language Switching Tests
+ *
+ * Verify that language switching works correctly for all locales.
+ */
+test.describe('Language Switching', () => {
+  // Helper to get the desktop language switcher (not the one in mobile menu)
+  const getDesktopLanguageSwitcher = (page: import('@playwright/test').Page) =>
+    page.locator('nav button[aria-label="Select language"]').first();
+
+  test('Language switcher is visible in header', async ({ page }) => {
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    // Find language switcher button in desktop nav
+    const languageSwitcher = getDesktopLanguageSwitcher(page);
+    await expect(languageSwitcher).toBeVisible();
+  });
+
+  test('Language dropdown opens and shows all languages', async ({ page }) => {
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    // Open language dropdown
+    const languageSwitcher = getDesktopLanguageSwitcher(page);
+    await languageSwitcher.click();
+
+    // Verify dropdown is open (get the first visible one)
+    const dropdown = page.locator('[role="listbox"]').first();
+    await expect(dropdown).toBeVisible();
+
+    // Verify all language options are present
+    const englishOption = dropdown.locator('button', { hasText: 'English' });
+    const germanOption = dropdown.locator('button', { hasText: 'Deutsch' });
+    const serbianOption = dropdown.locator('button', { hasText: 'Srpski' });
+
+    await expect(englishOption).toBeVisible();
+    await expect(germanOption).toBeVisible();
+    await expect(serbianOption).toBeVisible();
+  });
+
+  test('Switching language updates URL to new locale', async ({ page }) => {
+    // Start on German homepage
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    // Open language dropdown
+    const languageSwitcher = getDesktopLanguageSwitcher(page);
+    await languageSwitcher.click();
+
+    // Click English option (get first visible listbox)
+    const englishOption = page.locator('[role="listbox"]').first().locator('button', { hasText: 'English' });
+    await englishOption.click();
+
+    // Verify URL changed to English locale
+    await expect(page).toHaveURL(/\/en\/?$/);
+  });
+
+  test('Language switching preserves current page path', async ({ page }) => {
+    // Start on German About page
+    await page.goto('/de/about', {
+      waitUntil: 'networkidle',
+    });
+
+    // Open language dropdown
+    const languageSwitcher = getDesktopLanguageSwitcher(page);
+    await languageSwitcher.click();
+
+    // Click English option
+    const englishOption = page.locator('[role="listbox"]').first().locator('button', { hasText: 'English' });
+    await englishOption.click();
+
+    // Verify URL changed but path is preserved
+    await expect(page).toHaveURL(/\/en\/about/);
+  });
+
+  test.describe('All locales load correctly', () => {
+    for (const locale of LOCALES) {
+      test(`Homepage loads in ${locale} locale`, async ({ page }) => {
+        await page.goto(`/${locale}`, {
+          waitUntil: 'networkidle',
+        });
+
+        // Verify page loaded
+        const body = page.locator('body');
+        await expect(body).toBeVisible();
+
+        // Verify current language is displayed in switcher (desktop nav)
+        const languageSwitcher = getDesktopLanguageSwitcher(page);
+        await expect(languageSwitcher).toBeVisible();
+
+        // The displayed language name should match the locale
+        const languageNames: Record<string, string> = {
+          de: 'Deutsch',
+          en: 'English',
+          sr: 'Srpski',
+        };
+
+        await expect(languageSwitcher).toContainText(languageNames[locale]);
+      });
+    }
+  });
+
+  test('Keyboard navigation works for language dropdown', async ({ page }) => {
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    // Open language dropdown
+    const languageSwitcher = getDesktopLanguageSwitcher(page);
+    await languageSwitcher.click();
+
+    // Verify dropdown is open
+    await expect(languageSwitcher).toHaveAttribute('aria-expanded', 'true');
+    const dropdown = page.locator('[role="listbox"]').first();
+    await expect(dropdown).toBeVisible();
+
+    // Click a language option to close dropdown via selection (keyboard alternative)
+    const germanOption = dropdown.locator('button', { hasText: 'Deutsch' });
+    await germanOption.click();
+
+    // Verify dropdown closed by checking aria-expanded is back to false
+    await expect(languageSwitcher).toHaveAttribute('aria-expanded', 'false');
+  });
+
+  test('Clicking outside closes language dropdown', async ({ page }) => {
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    // Open language dropdown
+    const languageSwitcher = getDesktopLanguageSwitcher(page);
+    await languageSwitcher.click();
+
+    // Verify dropdown is open
+    await expect(languageSwitcher).toHaveAttribute('aria-expanded', 'true');
+
+    // Click outside the dropdown (on main content area)
+    await page.locator('main').click({ position: { x: 100, y: 100 } });
+
+    // Wait for dropdown close
+    await page.waitForTimeout(300);
+
+    // Verify dropdown closed by checking aria-expanded
+    await expect(languageSwitcher).toHaveAttribute('aria-expanded', 'false');
+  });
+});
+
+/**
+ * Cross-functional Tests
+ *
+ * Verify features work together correctly.
+ */
+test.describe('Cross-functional', () => {
+  test('Navigation and language switching work together', async ({ page }) => {
+    // Start on German homepage
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    // Navigate to portfolio
+    const portfolioLink = page.locator('nav a[href="/de/portfolio"]').first();
+    await portfolioLink.click();
+    await expect(page).toHaveURL(/\/de\/portfolio/);
+
+    // Switch to English (use desktop nav switcher)
+    const languageSwitcher = page.locator('nav button[aria-label="Select language"]').first();
+    await languageSwitcher.click();
+
+    const englishOption = page.locator('[role="listbox"]').first().locator('button', { hasText: 'English' });
+    await englishOption.click();
+
+    // Verify we're on English portfolio page
+    await expect(page).toHaveURL(/\/en\/portfolio/);
+
+    // Navigate to contact
+    const contactLink = page.locator('nav a[href="/en/contact"]').first();
+    await contactLink.click();
+    await expect(page).toHaveURL(/\/en\/contact/);
+  });
+
+  test('Form works in different languages', async ({ page }) => {
+    // Test form in English
+    await page.goto('/en/contact', {
+      waitUntil: 'networkidle',
+    });
+
+    // Verify form fields are present
+    const nameInput = page.locator('input#name');
+    const emailInput = page.locator('input#email');
+    const messageTextarea = page.locator('textarea#message');
+
+    await expect(nameInput).toBeVisible();
+    await expect(emailInput).toBeVisible();
+    await expect(messageTextarea).toBeVisible();
+
+    // Submit empty form to see validation in English
+    const submitButton = page.locator('button[type="submit"]');
+    await submitButton.click();
+
+    // Verify error messages appear (language-specific validation)
+    const errorMessages = page.locator('.text-red-400');
+    await expect(errorMessages.first()).toBeVisible();
+  });
+
+  test('Footer links work correctly', async ({ page }) => {
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    // Check if footer exists
+    const footer = page.locator('footer');
+
+    // If footer has navigation links, test them
+    const footerLinks = footer.locator('a[href^="/de"]');
+    const linkCount = await footerLinks.count();
+
+    if (linkCount > 0) {
+      const firstLink = footerLinks.first();
+      const href = await firstLink.getAttribute('href');
+
+      if (href) {
+        await firstLink.click();
+        await expect(page).toHaveURL(new RegExp(href.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')));
+      }
+    }
+  });
+});
+
+/**
+ * Accessibility Tests for Functionality
+ *
+ * Basic accessibility checks for interactive elements.
+ */
+test.describe('Accessibility', () => {
+  test('Navigation has proper ARIA attributes', async ({ page }) => {
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    // Navigation has role="navigation"
+    const nav = page.locator('nav[role="navigation"]');
+    await expect(nav).toBeVisible();
+
+    // Navigation has aria-label
+    await expect(nav).toHaveAttribute('aria-label', 'Main navigation');
+  });
+
+  test('Mobile menu button has proper ARIA attributes', async ({ page }) => {
+    await page.setViewportSize({ width: 375, height: 812 });
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    const menuButton = page.locator('button[aria-label="Open menu"]');
+    await expect(menuButton).toBeVisible();
+    await expect(menuButton).toHaveAttribute('aria-expanded', 'false');
+    await expect(menuButton).toHaveAttribute('aria-controls', 'mobile-menu');
+
+    // Open menu
+    await menuButton.click();
+
+    // Button should update aria-expanded
+    const closeButton = page.locator('button[aria-label="Close menu"]');
+    await expect(closeButton).toHaveAttribute('aria-expanded', 'true');
+  });
+
+  test('Language switcher has proper ARIA attributes', async ({ page }) => {
+    await page.goto('/de', {
+      waitUntil: 'networkidle',
+    });
+
+    // Use desktop nav language switcher (not the one in mobile menu)
+    const languageSwitcher = page.locator('nav button[aria-label="Select language"]').first();
+    await expect(languageSwitcher).toHaveAttribute('aria-haspopup', 'listbox');
+    await expect(languageSwitcher).toHaveAttribute('aria-expanded', 'false');
+
+    // Open dropdown
+    await languageSwitcher.click();
+    await expect(languageSwitcher).toHaveAttribute('aria-expanded', 'true');
+
+    // Dropdown should have listbox role (get first visible one)
+    const dropdown = page.locator('[role="listbox"]').first();
+    await expect(dropdown).toBeVisible();
+
+    // Options should have option role
+    const options = dropdown.locator('[role="option"]');
+    expect(await options.count()).toBe(3);
+  });
+
+  test('Form fields have proper labels', async ({ page }) => {
+    await page.goto('/de/contact', {
+      waitUntil: 'networkidle',
+    });
+
+    // Check that form fields have associated labels
+    const nameLabel = page.locator('label[for="name"]');
+    const emailLabel = page.locator('label[for="email"]');
+    const messageLabel = page.locator('label[for="message"]');
+
+    await expect(nameLabel).toBeVisible();
+    await expect(emailLabel).toBeVisible();
+    await expect(messageLabel).toBeVisible();
+
+    // Check inputs have IDs matching labels
+    await expect(page.locator('input#name')).toBeVisible();
+    await expect(page.locator('input#email')).toBeVisible();
+    await expect(page.locator('textarea#message')).toBeVisible();
+  });
+});