Git is quite confusing for the first few times, not gona lie. But simple commit and push should be doable.
You project is in Unity like many other including mine. I guess you could look at other Unity project submission repositories. What did they put in and such. For the most part it was just Assets and Packages folders.
Almost :)
You don't need to put them in zip archives. You should add folder itself. for example:
https://github.com/bryengx/GameOff2022
That way if you have someone else on the team they will be able to do changes to specific files or add more files. And all you would have to do to receive their changes is use pull comand.
I guess archives might still work out for one man team. :)
