Samsung Galaxy S4 Camera App broken?

I dropped my phone this weekend, and when i picked it up, all the lights on the bottom (so the arrow and the line thingy) and the little flashing led light were working, just the screen itself was not lighting up. so I went to my phone provider and they told me I needed the screen replaced or pay them 600$ to cancel my plan and buy a new phone, so I just got the screen replaced because I had just got the phone in March and it was cheaper and now everything is working except for the camera. When i load the app that came with the phone it just does this like looping greenish coloured thing. And at first the back camera would work on Snapchat but not the front camera, so i brought it back to the guy who changed my screen and now the camera doesnt even work on snapchat.I have attached a video of what it does when I open the app, also the purple light is just from the other camera, its not actually on the phone.
Please Help me.