How to connect SourceTree to an existing git repository on a foreign cloud (not Bitbucket)?

[Gerhard Heil]

Hi all,
we have created a git repository on a cloud server (not GitHub, Gitlab or Bitbucket), where we already have other data. Access to that cloud server is enabled via SSH public key / private key, we don´t have a login password for login via username and password.

The repo is accessible via git commands by url ssh://git@<ip address>/<path>.

When I start SourceTree 3.3.8, it requests to connect with Bitbucket (server) account, asking for the url and the login password.

I also tried SourceTree 3.3.6, where startup is passed. When I start SourceTree 3.3.6, it asks for the passphrase of my SSH key (that means it knows the correct SSH key). I entered the url in Settings -> Remotes, but both Pull and Push do not have any remote connection:

For Pull, I would need to select an item from "Pull from remote branch" ("vom entfernten Zweig pullen" in German language), but the branch list is empty. And in Push, I would have to select an entry in the list of pushable branches ("Zu pushende Zweige" in German language), but also that list is empty.

How can I connect our repo, either in SourceTree 3.3.6 or 3.3.8?

Thanks and best regards
Gerhard