Need Help Cleaning my repo, max space exceeded

Hello everyone,
I am really lost, and have been searching online any solution,
my gitlab repo just exceeded the 10go limit by 500 Mo, we are making a video game as a student project.
And I first wanted to see if we could increase the space, but it seems impossible even with money,
so I search how to clean up the repo, but deleting files won’t work because the push is automatically declined because of the exceeding limite.
And I have been looking for other ways, but everything I see I can’t understand.
I tryed Housekeeping button, but other than sending me to the repo It does nothing,
Does anyone know what I could do?
Thanks