My next question:

How to reset a “View” that I accidentally set incorrectly with titel "promoted content" (see screenshot) or better: how to bring "all views" back to origin point after installing backdrop?

Screenshot

Comments

From within the view:

From the listing of views:

I'm not aware of a simple way to revert all views to their default in one operation. 

There were already questions about Views restoration to default settings, but I did not see a simple answer — install a clean copy of Backdrop and make an export > import. I always have a copy Backdrop “for experiments” on a local server, very convenient.