We don’t actually support Mac OS sorry!
I’m not familiar with tech support for Macs, but generally for this sort of issue on PC we would suggest turning the graphics settings to low and checking RAM and CPU usage while the game is running to see if the hardware is handling the game ok or what is causing the issue exactly.
If you receive any error messages you can also let us know as that will help pinpoint the problem (especially if it’s an in game error message rather than a Mac OS error)