_Dagobert_Duck

So, 
I solved the problem on my own and I do not want to prevent you from seeing it:
So, I found out that there is a download for macOS in the "Download" section (what a cognition!).
I installed this file on my Mac (MacBook Pro 2021 16 inch base model) like any other app. But I had to change something in the config of the game, because as I were in-game, the GUI and the tool bar were hidden if a block outline was shown. So for that, open finder, press  command + shift + .  , open .config/VintagestoryData and open the "client settings.json" file. In that, change the boolean selectedBlockOutline from true to false. That's it.
Happy Playing,
Scrooge