Want to change the database structure of gitlab (add some fields)

I want to use gitlab as a code repository inside our school, but considering that I need some additional user information to mark students (such as student numbers, which is easy to rate at the end of the semester), I need to know what can be done?

I am a student. This is a development task that my professorarranged for me. I am also very interested in it, but I can’t start.

I just started to contact gitlab, I hope someone can answer my doubts.