When do you do descent checklist to the line?
The first item is altimeter setting. The transition altitude in Germany is 5000 feet.

We have the same problem in the UK where transition altitude is 6,000ft. I do "descent checklist to the line" using 1013 shortly after starting the descent, and do "below the line" passing below FL100. I say "xxxx set, crosscheck" again, at transition altitude, but this time using QNH.