Dear Muztaba,
I can see that you have uploaded an SSH public key, but it does not appear to be used for login. If your private key is not in a standard location and/or does not have a standard name (such as, e.g., ~/.ssh/id_rsa), then you have to specify it explicitly upon login:
$ ssh -i ~/.ssh/id_rsa_myspecialnewkey ptfs138h@fritz.nhr.fau.de
Could this be the problem? You can also send the diagnostic output of the ssh command if you add the "-v" option.
Best,
Georg.