I would suggest you only put your games source code into git, and use other means to archive assets. Git is not good at all with binary files, I think it doesn’t even attempt to save just differences. If you change a 500 MB asset it will add another 500 MB to your repository. For every single change again. Maybe even for a change in file attributes.
Put your content folder in a 7zip archive f.e., you could make a script that compresses it and tacks the current date to the archive filename; or the current git hash you are at.
BTW what do you mean with you can upload folders separatly? How do you push parts of an repo??