Make sure to quit all other open apps. Games generally need to be the only app running.
Are you running any anti-virus software, cleaning/optimizer apps, or third party security software? If so, then uninstall them by following the developers' instructions. These types of apps are not needed on a Mac and usually causes more problems than they solve because they interfere with the normal operation of macOS. Plus they tend to impact system performance.
You may also want to try disconnecting all external devices in case one of them is causing a problem.
You may also want to check the game's forums to see if any other Mac users are encountering problems. And you can try contacting the game store support where you purchased the game for assistance. I believe that Feral Interactive is the developer who ported the game to macOS so they may be the ones you need to contact for support regardless of where the game was purchased.