35gb of photos even though i only have 7000 photos in my phone

Hi, around 4 months ago, I purchased 50gb plan for icloud and after a month i suddenly got 35gb of photos stored in my phone(??)

How did that happen? I synced my old iphone with this icloud, but on both phones together, there is no more than 7500 photos and not many videos. How is that even possible?

Last night i tried deleting a lot of media from my old phone, since it is synced with this icloud I thought that would help but nothing happened. Storage on my main phone is still full. I can't even see the structure of those 35gb and I don't know what to do.

Would appreciate any help, thanks!!