I actually got it working, but it isn't plug and play!
Step 1: Open terminal
Step 2: type chmod +x
Step 3: Drag the file you find in: "Left click on the game -> Show package contents -> MacOS" to the terminal and press ''enter''.
(!) Dont't use ''enter'' between the chmod +x command and the file you want to drag.
This will make the file an executable file, which makes it possible to boot up the game.
The problem is that the Mac doesn't recognise the executable file on default.