o.k. .. I see ... gives more work but more flexibility.
Now, I have an access rule on the admin-folder with page protection.
If AccessLevel of Session =! 10 redirect to login page. There I put an error message "You don't have access to this page".
This works if I call "website.com/cms/admin" directly without login, so redirect to login page works and the error message appears on the login page.
But the error message also appears, when I just call the login page.
How do I solve this? Thx for any help in advance.