Why is my gaming laptop running/performing slow?

I have a Lenovo y50 "gaming laptop". I've had it a little over a year. It was made in 2013 I think. I don't remember the exact specs. But if you want to look them up it is the Lenovo Y50 (not the touch screen). The specs were pretty good. I've only played 2 games on it. MineCraft and now H1Z1. I mostly use it for making/editing YouTube vids and Internet browsing. But minecraft runs great on it. But H1Z1 sometimes runs smooth as butter but more times then not, it runs bad and "choppy". Like when I hit the interaction keys (like "tab" and "e") the whole screen/game freezes for a couple seconds. And it's laggy a lot when not hitting those game interaction keys. I've tried putting it on "high performance". By hitting the battery icon and putting it on high performance instead of balanced. And tried playing when there's NO other program running. I'm running the game on high settings. Not ultra settings tho. And it's lagging this bad on high game settings. Don't want to turn them down bc the quality of the game isn't as good. And other settings I can tweak or any suggestions? What do you think is going on? (I'm not a big computer guy in the sense I don't know a lot of computer slang or how to do things "setting" wise without instructions so please help me!) a thanks for the help!