Can't connect computer to GitLab via cmd

I’m a computer science student, and our university uses it’s own GitLab server - in other words I thinks it’s self managed. This has led to som issues regarding my GitLab setup and furthermore connecting the ssh-keys to GitLab and so on. I have issues pushing from CMD, however I am able to do so from GitKraken, and inside IntelliJ. I am not able to test my connection to GitLab using the ssh -T command. See picture beneath.
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When using the -Tv command I get connection established, however some errors as well. See picture.
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Further debug information:
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Just to clear up - I am typing my passphrase, but CMD hides it. This is also copied from where I have it stored, so it’s not a typo issue.

I will appreciate any help!