Unity crashed while building, now it crashes everytime I open the project.

Unity crashed while building, now it crashes every time I open the project. Even when I open a older backup scene file I worked on an hour ago, to test if it’s the scene and it still crashes. What’s going on? Is there a way to restore my project and scenes?
Was working on a UI project.

Help please!

EDIT: I fixed it. I copied the project files to another project folder and it works now. I still don’t know what caused the crash though.