How to return everything back to my iphone

Hi !

I really hope you can help me!

Namely, I wanted to transfer pictures from my iPhone X to the computer. Since I'm not really an expert in that area, I asked a friend to do it. Instead of transferring the pictures, it transferred the 2018 backup from my old iphone 7. Now everything from my iphone X is deleted and everything from the iphone 7 is copied to iphone X.

How do I undo it??

Please help !