hi, @DesertRose. It is highly recommended to use one branch for each change/feature you want to make.
On windows I mostly use Git Bash (it's console) but for some stuff I use GitExtensions https://gitextensions.github.io/
I hope this can help you, last comment.:
Oh, I think I see. I'll start with a change like this: https://gitea.wildfiregames.com/0ad/0ad/commit/2d43ca6462940e9c3aad82309e41febb53892654?files=binaries%2fdata%2fmods%2fpublic%2fmaps%2frandom%2ffrontier.js