My iPhone tweaks all the time after replacement of screen

So about 2 months ago I got my screen replaced at a swap mart for 50 bucks. 2 hours after I took my phone home the screen always did things by itself. For example it types by itself or if I'm playing a game like subway surfers then it does it's own moves and I end up crashing what do I do. Sometimes it clicks things by itself or doesn't allow me to click things like the zoom in button on YouTube and stuff like that

Facebook Messenger Crashing on iOS 11?

I just updated my iPhone 7 to iOS 11 and every time I try to start up Facebook messenger it crashes n me. Has this happened to anyone else? Does anyone know how to fix this?