Fixed translation links in mobile menu not working properly; improved translation

public/en/404.html

@@ -123,11 +123,11 @@
         <hr />
         
           <li>
-            <a href="/en/">English</a>
+            <a href='/en/404.html'>English</a>
           </li>
         
           <li>
-            <a href="/de/">Deutsch</a>
+            <a href='/de/404.html'>Deutsch</a>
           </li>