Why can't I access my camera anymore on iPhone?

After I updated my iPhone 4S to 8.3 version from 7.9 version, I started to have some problems with it. First of all, I can't access my camera (photos or videos). I press on the camera and nothing happens. Only black screen. If I press to make a photo or to record a video, nothing happens again, not on the back camera and neither on the front camera. Secondly, I also have some problems with the phone that like 1-2 times in 2 days, it blocks and I can't make anything on the phone. Therefore I'm forced to restart my phone. After I shutdown my phone. I need to wait like 10 minutes to open it again because it opens it, I hear some sounds from it but I can't see anything on the screen. I'm 100% sure these problems appeared because of the update because when it was to 7.9 version I didn't have any of these problems.