Hi Andreas,
I recommend to do the provided tutorials in the academy, there every aspect of creating an Mendix App using MindSphere is explained.
See here:
https://academy.mendix.com/link/path/80/Build-a-MindSphere-app-with-Mendix
and here:
https://academy.mendix.com/link/path/93/Build-a-MindSphere-App---Continued