My phone dies really quick and gets burning hot

I have an Iphone 4 and when i charge my phone it gets really hot like along the silver parts and burns also my battery dies really quickly i don't know if those are related... My phone goes from about 100% to died in about 15min it also takes many hours to get to 100% when my phone is hot i also get this weird purple glow around a picture when i try to take one I found this out using Snapchat and it isn't a filter because it's with my normal camera too i don't know what the problem is if my phone is broken or if i just need a new battery if the problem is because of the battery i just don't know please help 😀