Today, mechanic Konrad removed the battery cables from my car at his workshop, cleaned them with a wire brush and sandpaper, lubricated the contacts with petroleum jelly, and then reconnected the cables to the battery.
The photos show the before and after cleaning.





I was a bit worried about whether the car would start without any problems, but it turned out the engine started without any problems.
However, after driving a short distance, the BAS/ESP light on the dashboard came on...
I read in the manual that I should perform the following calibration:



When I was ready to perform this procedure, the BAS/ESP light went out on its own and has since stopped flashing.
Maybe this will be useful to someone.