diff --git a/themes/fid_adlr/scss/_customMixins.scss b/themes/fid_adlr/scss/_customMixins.scss
index 49fbe9b9592578ef6465699f9851c092383d104c..b38de9685cc5a2eb8b33d0e99ef883c3c0e21c3f 100644
--- a/themes/fid_adlr/scss/_customMixins.scss
+++ b/themes/fid_adlr/scss/_customMixins.scss
@@ -172,10 +172,31 @@
 
   @media screen and (max-width: $screen-md-max) {
     height: 100%;
-    padding-top: $navbar-default-padding;
+    padding-top: 15px;
     width: 9999px;
   }
 
+  // workaround for landscape and firefox
+  @media screen and (max-width: $screen-sm-max) and (orientation: landscape) {
+    height: 500px; // height needed
+    overflow-y: scroll;
+
+    .submenu-collapse {
+      height: 700px; // height needed
+    }
+  }
+
+  // workaround for landscape and firefox
+  @media screen and (min-width: $screen-md-min) and (max-width: $mobile-navigation-menu-breakpoint) and (orientation: landscape) {
+    height: 800px; // height needed
+    overflow-y: scroll;
+
+    .submenu-collapse {
+      height: 1100px; // height needed
+    }
+  }
+
+
   @media screen and (min-width: $screen-sm-min) {
     padding-top: $navbar-extended-padding;
   }
diff --git a/themes/fid_adlr/scss/compiled.scss b/themes/fid_adlr/scss/compiled.scss
index f81994ba43aa575e053f541dbfdd6497e2822a5e..2b737af8ddb3cf32c93d4690b12096e3c4633c24 100644
--- a/themes/fid_adlr/scss/compiled.scss
+++ b/themes/fid_adlr/scss/compiled.scss
@@ -650,6 +650,16 @@ header,
       }
     }
 
+    @media screen and (max-width: $screen-xs-max) and (orientation: landscape) {
+      left: 375px;
+      top: calc(#{$navbar-header-height} + 10px);
+    }
+
+    @media screen and (min-width: $screen-sm-min) and (max-width: $mobile-navigation-menu-breakpoint) and (orientation: landscape) {
+      left: 750px;
+      top: calc(#{$navbar-header-height} + 2 * #{$navbar-default-padding} + 15px);
+    }
+
     @media (min-width: $mobile-navigation-menu-breakpoint + 1px) {
       border: 2px solid $asphalt;
       left: 0;
@@ -693,6 +703,16 @@ header,
     left: calc(#{$logo-max-width} / 2 + #{$navbar-margin-left});
     top: calc(#{$navbar-header-height} + 9 * #{$line-height-submenu} + 10 * #{$navbar-default-padding});
   }
+
+  @media screen and (max-width: $screen-xs-max) and (orientation: landscape) {
+    left: 375px;
+    top: calc(2 * #{$navbar-header-height} - 25px);
+  }
+
+  @media screen and (min-width: $screen-sm-min) and (max-width: $mobile-navigation-menu-breakpoint) and (orientation: landscape) {
+    left: 750px;
+    top: calc(#{$navbar-header-height} + 5 * #{$navbar-default-padding} + 5px);
+  }
 }
 
 .header-menu-collapse {
@@ -709,7 +729,7 @@ header,
         position: absolute;
         z-index: z-index(navigation-overlay, 0);
       }
-      .submenu-collapse {
+      .submenu-collapse-wrapper {
         position: absolute;
         top: $navbar-header-height-home-sm;
       }
@@ -717,7 +737,7 @@ header,
   }
 
   &.collapse:not(.in) {
-    .submenu-collapse {
+    .submenu-collapse-wrapper {
       background: $white;
       height: 0;
       padding: 0;
@@ -728,7 +748,7 @@ header,
 
   &.collapse.in,
   &.collapsing {
-    .submenu-collapse {
+    .submenu-collapse-wrapper {
       @include navigation-overlay;
       @media (min-width: $mobile-navigation-menu-breakpoint + 1px) {
         position: absolute;
@@ -741,7 +761,7 @@ header,
 .header-menu-collapse.collapsing {
   padding: 0;
 
-  .submenu-collapse {
+  .submenu-collapse-wrapper {
     @media (max-width: $screen-sm-max) {
       background-color: $white;
       padding: 0;
diff --git a/themes/fid_adlr/templates/header.phtml b/themes/fid_adlr/templates/header.phtml
index 13822770d31522d6864b8ba50b5d14e56171d4c1..0c8bbaaf2b50a28b753d1a194722cf828ea1f56f 100644
--- a/themes/fid_adlr/templates/header.phtml
+++ b/themes/fid_adlr/templates/header.phtml
@@ -162,6 +162,7 @@
     <!-- fid_adlr: basic header menu for submenu toggler - END -->
 
     <div class="collapse header-menu-collapse" id="submenu">
+      <div class="submenu-collapse-wrapper">
       <ul class="submenu-collapse">
         <li>
         <?php $searchOptions = $this->searchOptions("Solr"); ?>
@@ -190,7 +191,8 @@
         <li>
           <a href="<?= $this->config()->get('config')->RssConsumer['fallback_url'] ?? ""?>/service-fuer-fachreferate" target="_blank"><?=$this->translate('Services for subject specialists')?></a>
         </li>
-      </ul>
+
+      </div>
     </div>
   </nav>
   <!-- fid_adlr: navigation - END -->
@@ -244,6 +246,16 @@
                 $('#language-dropdown').collapse('hide');
             }
         });
+
+        $(document).on('click','#submenuToggler',function(){
+            if($('#submenu') && $('#search-main-dropdown').css('display') != 'none' && $('#submenu').attr('aria-expanded') == 'true') {
+                $('footer').hide();
+                $('#main').hide();
+            } else {
+                $('footer').show();
+                $('#main').show();
+            }
+        });
     });
 </script>
 <!-- fid_adlr: header - END -->
\ No newline at end of file