Please perform the below mentioned steps to resolve the issue:
> Stop the background running app (Tap on the left soft key and close all the running apps).
> Ensure 20% of internal memory of device is free (Scroll down notification panel > Setting > Device maintenance > storage).
> If device lags in any particular application/game then clear cache memory of that application (Settings>apps> tap on that app>storage>clear cache)
For further assistance, register your concern in Samsung members app (Open Samsung members app>click on “+“icon>send feedback>Error report/ Ask Questions).
Team Samsung Members