GIT - connection keeps asking to add ssh-server key and for password

Everytime I try to push or pull something to/from my GIT-Server, PHPStorm asks me to add the ssh-server key to the known-hosts file (where it IS already available). I tried to use the native ssh, but then GIT fails completely.

Plus: GIT also asks for my GIT Password everytime I push/pull

None of the solutions that I found in the forums did help.

Using OS-X High Sierray with PHPStorm