Failed to load scene after copying project

Hi!
After I have exported a project file to a friends laptop he opened the project, but failed to load the scenes. We had this problem before. It is the first time working on a team so we don’t have much experience on that. Can any of you recommend a software like github that is compatible with unity? Is there any way how we can restore the scenes? Luckily we made backups, but there is still valuable work lost…

Fixed it. It was because we used the wrong versions of unity and had OS differences:)