@Mykle1
Hi!
Thanks for the quick reply!
It didn’t work out that way. I found a documentation on:
https://stackoverflow.com/questions/21564275/windows-shortcut-to-run-git-bash-script

So, I generated a script C:\Users\USER\npmstart.sh with

cd ..
cd ~/MagicMirror
npm start

Afterwards I generated a shortcut on the desktop with following path:
"C:\Program Files\Git\bin\sh.exe" -l -i "C:\Users\USER\npmstart.sh"

And it works. It starts the Bash and runs MagicMirror and leaves the Bash open in the background, so I can get back to it by pressing the Windows-Button. (remember, I run the MagicMirror on a tablet without keyboard and mouse)
In the Bash, I can stop MagicMirror with the onscreen keyboard by pressing Ctrl+C.

Regards
womi