iPhone 3GS randomly dying and camera freezes on shutter screen

I have an unlocked iPhone 3GS. When I got it, it worked fine but anoint a month after, the battery started dying randomly. At first or wasn't that big of a problem because it would die at 10-20% but now it's dying at 90-95%. Any way to fix?! And also my camera has started freezing on the shutter screen and will not work. Any way to fix that also?!