Godot backup and re-import proper way

Having a huge problem. Been working on a project with C#.
The project was deleted by me, and I thought I could just re-import the zipped files from the whole project.

I ask this question, because of my previous problem:

So my question is: what is the fool proof way to backup a C# project in Godot?

Most developers use git (and host on platforms such as github) or perforce.