Q: iPhone 5s back camera not working with black screen?

I've seen a couple questions which are similar to mine but none of the answers helped so I would like some advice catered to myself.

Anyways, so I got an iPhone 5s secondhand from a friend who had reset it to factory settings for me. I know that everything worked for her before. Whenever I open the camera, the back camera shows a black screen and when I switch to the front camera that one works but changing it back to the back camera will result in a really blurred image of what was on my front camera and then I won't be able to click anything, not my photos, the filters or the capture button. The flashlight also does not work at all.

I've opened the camera up in multiple apps such as SnapChat and Instagram but all they show is the front camera with no option to even change to the back cam.

Help??

I've reset the phone 4 times and still nothing.