Hi Constanza,
Thanks for reaching out. I assume that you are using the ‘regular’ git version control. As git is something else than GitHub, I would like to advise you to read the article below. It shows you how to use your own repository. If you follow these steps with GitHub, you should be able to manage the repository yourself. Now your project is on the Mendix Teamserver, following the git versioning system.
https://docs.mendix.com/refguide/on-premises-git/
Hopefully, this helps!