CAfile: none, SSL and Security Question

Hello,
since im pretty new to gitlab im no quiet sure what to do.

I’ve installed Gitlab-Omnibus 12.4 version and set up the path to my ssl-cert (.pem) and key-file in the gitlab.rb.
Everything works fine with the web-applikation however if I use git clone for Example it shows:
server certificate verification failed. CAfile: none CRLfile: none.
In addition to that curl gives mer Error 60.

So im wondering why this error occures. Especially because of “CAfile: none”. There are several topics about ssl Errors but the always got atleast a CAfile.

So if I copy the certificate (.pem) manually to a linux client in /etc/ssl/certs it works with git commands (e.g. git clone https://url). Would that be considered secure? Any hits where the problem ist?

Thank you in advanced