Casper
The following definitions are incorrect. You have translated "documents" to "dokumenter".
$_lang["access_permissions_dokumenter_in_group"]
$_lang["access_permissions_dokumenter_tab"]
$_lang["access_permissions_no_dokumenter_in_group"]
Should be
$_lang["access_permissions_documents_in_group"]
$_lang["access_permissions_documents_tab"]
$_lang["access_permissions_no_documents_in_group"]
Correct this and everything should work as expected.