Q: iPhone 6s get hot after 1-2 minute. Battery drain out. Getting hot without doing anything. Lagging.

I brought my 6s in January. For some reason it getting hot between Feb to now, like when I wake up and check my Facebook for 1-2 minute and it can get extremely hot and the battery drain out so quickly. Sometimes I even experiment it just get hot without doing anything.  Also I was experiment with lagging, sometimes it was force to reset, or just blackout and make me so worry. The lagging part is the worst. It can get froze forever until I am hard reset it. My family was an "Apple" type of family, and none of them actually experiment like I am. I was about to brought it in February but you know, let give it sometimes, and now I'm regret it. Anybody could give a suggestion? I try almost everything on the Internet.