@mariosipad
Crazy: as I could see all calibre-web categories entries at xxxxx.freemip.com at the website from the PI but not at my dektop PC I found out that I blocked pages by Adblocker
Now it works perfect (slow, but perfect)
As already mentioned I setup users with restricted permissions and login-data
Tahnks again for your comprhensive help - is there something I can offer you for a coffee-break? Via PayPAL?