Hello,
you used the wrong user>>> it is filtern not filter
I created an article which is called "59 OF A - Taschenorgan"
This article got the category "Lektion 59"
It is for users with access to level "59"
Since your user account has got Super Administrator rights, it has got access to this level. (I tried it).
I created a menu item (category blog) in Menu "Deutsch" called "C-59" .
I also created a menu item (single article) in menu "Deutsch" called "59 Taschenorgan".
I indexed all.
Using another browser with cleared cache, there is still the text from the homepage underneaf.
Thanks
Joerg