Theme - Git Clone Problem/Error

Hi im totally new to Hugo and Site Generators in general. I installed hugo and wanted to setup a new site with a theme, to see how everything works. After I created a new site I wanted to add a theme, but theres always a problem that occurs. Can someone help -->
I tried with different themes, but its always the same:

         { themes }  » git clone
            Cloning into 'hugo_theme_robust'...
            fatal: unable to access '': error setting certificate verify locations:
              CAfile: /etc/pki/tls/certs/ca-bundle.crt
              CApath: none

HI @Patrick22, that is more a git error I think.

The Problem was the Babun Bash I used. With Git Bash or CMDer it works