I have just checked your tenant logs and do see the Callback URL mismatch error. It specifically mentions that your https://www.tyfsl.de URL is not in the list of allowed callback URLs for your TYFSL application. When checking this, I can confirm that it is not in the list of Allowed Callback URLs.
After you have included the URL into your list of Allowed Callback URLs, you should be able to log in and redirect to the callback URL correctly.
thanks for your answer.
When I check the list, the URL you mentioned is in the list of allowed callback URLs.
There are 4 URLs in this list and the last one, ist the one you mentioned.