Xbox one game share with CD?

A friend of mine has an Xbox game, which I would like to test on my Xbox. He has the game as a disc. What happens if I just put the disc in my pocket and start it? Is his data deleted? Is something overwritten? Can he then continue to play normally at the point where he was?

As far as I know, the storage status is not stored on the disc but on his XBox…

Nothing changes with him, he just can't play without a disc in time.

So his storage stocks are preserved?

How is it if I get the game too? Do I have to start all over again?

Yes it stays that way and no you don't have to start over.