I accidentally deinstalled the Google app—now my phone doesn’t boot anymore
The actual solution was quite easy:


Power down the phone by long pressing the Off button
Boot the phone into fastboot mode by pressing On and Volume-Down
Select “Factory Defaults”
See Android booting again, having preserved all of the installed apps; only the Home screen had been emptied—oh, sure, I had deinstalled the Home screen app. That’s how the whole story began.