Issues with War for the Overworld on macos

Hello there!
I purchased War of the Overworld recently on Steam. But the game does not really work on my Mac. It begins with graphic glitches in the menus, the screen flickers from time to time, buttons are not visible. And when the game starts, it is impossible to select tiles or creatures. This clearly is a bug.
My configuration is:

Can you help me? Otherwise I will have to give the game back and ask for a refund. However, I would really love to play the game since I was an avid fan of Dungeon Keeper 1 and 2 (I have them both in my poassession, but they won’t run anymore via WINE now that I have updated my Mac - which actually brought me to have a look at WFTO).
Thank you for your help.