Why my phone gets smooth everytime I recieve notifications or if I press the task manager button?

[Android Central Question]

Hello, I have my Samsung Galaxy J7 Prime 2016. I had it for like a year now. I love playing games on my phones. I bought this phone because I saw how good it is. But I was wrong...

I play PUBG Mobile (Player Unknown's Battlegrounds) on my J7 Prime 2016. My game is not smooth at all. It really lags! But I discovered something....

Everytime I press the task manager button (basically on the left side of the home button) and I put it back on my game, it lags for a second, then it becomes soooo smooth!! Then after 3 seconds, it will become so lag again! It also happens when I get a notification.

If anyone can fix my problem then it'll be great!!

Thanks in advance!

 

[Rukbat]

When you finish using an app, do you use the Home button (bad) or the back button (good)? Using the Home button leaves the app running, even though you go back to the home screen. Using the back button means that Android can kill the app if it needs more RAM - which it evidently does for PUBG.