Iphone camera/photo problem?

I recently bought a used iphone 5s from someone. The camera app opens fine except it just shows a black screen with the capture buttons at the bottom. And it shows a picture in the small picture gallery thing but when i click it, it says there arent any pictures. I checked the storage and it says there's about 1gb of photos/videos but they don't show up when i open the photo app! I just want to clear that extra space from the phone but i don't know what to do.

Restore the phone through iTunes, which actually from the sounds of things, should've been done prior to it being sold.

Not sure if that would solve why the camera doesn't seem to be loading though. I would make sure I can still contact that person that sold you it in case you need to get a refund.