fix php version, lang files, basic tpl and sales impl.

Theme/Backend/Lang/de.lang.php

@@ -4,6 +4,7 @@
  *
  * PHP Version 8.0
  *
+ * @package   Modules\Localization
  * @copyright Dennis Eichhorn
  * @license   OMS License 1.0
  * @version   1.0.0

Theme/Backend/Lang/en.lang.php

@@ -4,6 +4,7 @@
  *
  * PHP Version 8.0
  *
+ * @package   Modules\Localization
  * @copyright Dennis Eichhorn
  * @license   OMS License 1.0
  * @version   1.0.0
@@ -13,7 +14,7 @@ declare(strict_types=1);
 
 return ['Media' => [
     'Account'          => 'Account',
-    'Add'              => '',
+    'Add'              => 'Add',
     'AddToCollection'  => 'Add to collection',
     'Author'           => 'Author',
     'Back'             => 'Back',
@@ -30,7 +31,7 @@ return ['Media' => [
     'Extension'        => 'Extension',
     'FilePath'         => 'File Path',
     'Files'            => 'Files',
-    'GroupUser'        => '',
+    'GroupUser'        => 'Group User',
     'Media'            => 'Media',
     'Name'             => 'Name',
     'Path'             => 'Path',

Theme/Backend/media-single.tpl.php

@@ -30,7 +30,7 @@ echo $this->getData('nav')->render();
             <?php if ($this->request->getData('path') !== null) : ?>
                 <a tabindex="0" class="button" href="<?= UriFactory::build('{/prefix}media/list?path=' . ($media->getId() === 0 ? $media->getVirtualPath() : '{?path}')); ?>"><?= $this->getHtml('Back'); ?></a>
             <?php else: ?>
-                <a tabindex="0" class="button" href="<?= UriFactory::build('{/prefix}media/list'); ?>"><?= $this->getHtml('Back'); ?></a>
+                <a tabindex="0" class="button" href="<?= $this->request->getReferer() !== '' ? $this->request->getReferer() : UriFactory::build('{/prefix}media/list'); ?>"><?= $this->getHtml('Back'); ?></a>
             <?php endif; ?>
         </div>
     </div>