current working configuration added

mymodule/themes/fancytheme/default/_footer.twig

   <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
   <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
   <script src="/js/headfoot.js"> </script>
+  <script src="/js/mobile.js"> </script>

mymodule/themes/fancytheme/default/base.twig

@@ -8,7 +8,7 @@
     <link rel="stylesheet" href="{{ asset("css/stylesheet.css") }}">
     <link rel="stylesheet" href="/css/bootstrap.min.css">
     <link rel="stylesheet" href="/css/m4lab.css">
-    <link rel="stylesheet" href="/css/Login-Form-Clean.css">
+    <link rel="stylesheet" href="/css/m4lab-mobile.css">
     <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.8.2/css/all.css" integrity="sha384-oS3vJWv+0UjzBfQzYUhtDYW+Pj2yciDJxpsK1OYPAYjqT085Qq/1cq5FLXAZQ7Ay" crossorigin="anonymous">
     <link rel="icon" href="{{ asset("icons/favicon.ico") }}">
     {% if isRTL %}

mymodule/themes/fancytheme/multiauth/selectsource.twig

@@ -10,7 +10,7 @@
     <h2>Benutzerkonto auswählen</h2>
     <p>Bitte wählen Sie ein Benutzerkonto aus, mit dem Sie sich authentifizieren wollen:</p>
 
-    <form action="{{ selfUrl|escape('html') }}" method="get">
+    <form action="/{{baseurlpath}}module.php/multiauth/selectsource.php" method="get">
         <input type="hidden" name="AuthState" value="{{ authstate|escape('html') }} ">
         {% for key, source in sources %}
             {% set name = ('src-' ~ source.source64) %}