Gitlab Build Runner on Windows uses HTTP instead of SSH

I am new to Gitlab CI but have been reading on the topic for a while now. I have to test-compile C#-Projects on my Gitlab after every commit and found out that I need to use a Windows Shell-Runner setup for CI to build my project correctly.

Unfortunately, my Gitlab setup only allows developers and machines to connect over SSH, not HTTP. But my Windows runner always tries to connect over http and fails the build. How can I configure it properly? I already tried to edit the config.toml associated with the runner, but there is no option to specify whether to use ssh or http.

Thanks in advance!