Android
When the notification pops up, simply long press on it and App info will pop up. Tap on that, and you’ll be taken straight to the app management screen where you can uncheck the Show notifications box. It does mean that all notifications from that app will be turned off. As the warning states “If you turn off notifications for this app, you may miss important alerts and updates.

iOS
It is simple to do if you follow these recommendations:
- press on "Setting" on you phone,
- choose " Notifications",
- tap on the game,
- and move button on "off".