Tried replacing battery now randomly opens apps

I tried replacing my battery on my iPhone 6s Plus. Followed every step as directed and after I got the phone back together it works and the battery charges but after a couple of minutes go by it starts to open apps, dials phone numbers, keyboard appears and starts typing, etc… it’s like it goes haywire. When I turn off the screen then turn it back on it’s fine for a few minutes then starts going haywire again. Tried taking it apart and reconnecting it but still has the same problem. It is difficult to tap icons and to type because it’s not as sensitive to the touch as it use to be. Can’t figure out what the problem is?