I have driven a number of Mercedes and Audis, and they have taught me a lot about the stereotypes of Germans. Like most stereotypes, there are elements of truth contained.
You must work on these cars "in the way of correctness". There is a correct way to do things, and Audi and Mercedes require it. Depart from it at your peril. The result is superb cars that are wonderful to drive.
But - if they decide that the correct way to install a glove box is using six different types of screws, all of different lengths, then they do so. And you better get each screw back in the hole it came out of, or bad things could happen - no kidding.
My dad did a valve job on his '59 Mercedes 219. When reassembled, he noticed that one metal clip on the fuel line had not been secured by the timing cover bolt next to it. He figured "...no problem, I'll start it, let it cool, then secure the clip when I re-torque the head."
But the car wouldn't start. Why?
Because (if memory serves) THAT clip had to be under THAT bolt, and THAT bolt had to be the CORRECT bolt of the CORRECT length, because the length of the bolt (minus the thickness of the metal clip) extended to the tensioner for the timing chain, and had to push against the tensioner for the chain to be properly tensioned.
Or the car would not start.
On a US car, most mechanics would probably have thrown the clip away, but on that Merc, it was a critical part of the timing chain adjustment.
I learned much about Deutschland from that experience.