Cannot see game scene but can access project files

I am new to Unity but a friend of mine already has some experience, we decided to collaborate to a project he started some weeks ago, I installed his version of Unity (5.6.4p2, 2017) on my PC and then I tried to access the project, I can read and edit all the files but I cannot edit or play the game itself.
Before, I also tried with the latest version (1st July 2020) and I had the same issue, I thought it was due to the huge difference between the two versions but it wasn't.
We both use Windows 10.

 

Hi @Just_ABoy, welcome to Unity! When you first download a project from Collaborate you are shown an empty sample Scene. You can think of a Scene in Unity like a level in a game. You'll need to open that level in the Unity Editor before you can play it. Try searching for a .scene file in the Project. If there isn't one, have your friend double check that they published their Scene that they're working in and that you're able to open it.

 

Hello...
After working on for so long i finally finished my project in unity... but somehow was wondering what's the SampleScene for and double clicked on in, it opened a scene only with lights on it - there's nothing else... There is no way I can bring my project back. A week ago I made a copy of the whole folder just for any case - even after opening my older project there's nothing on it.
I'm extremely sad!