Hi @rugdug,
Try using the phone in [https://www.techjunkie.com/samsung-galaxy-j5-turn-safe-mode-on-or-off/|safe mode] and check if it works better.
If it does a ''downloaded'' app is the cause of the problem. You will need to uninstall each ''downloaded'' app, one by one and test the phone in normal mode between each uninstall to see if it works OK. When it does the last ''downloaded'' app that was uninstalled was the culprit. A downloaded app is one that you downloaded and installed onthe phone and wasn’t pre-installed on the phone when you first got it.
Also if it only happens on one game it may be that the phone doesn’t have the system resources to play it properly so it glitches or freezes because it can’t cope.