Mark airspace – build closed directly (approx. 6–7 m²)?

That is theory from your "Project Management for Beginners" guides, but has very little to do with reality ;)
Accordingly, anyone who has ever paid a craftsman under the table would mentally be seen as an evil criminal who is also capable of quite other misdeeds...

Tell me, do you sometimes drive 52 in the city instead of 50? :D

I see black market payers the same way you describe it there. That is criminal and rightly punished severely. Working off the books is not a minor offense but a crime to the detriment of all.
Unlike exceeding the speed limit within the range mentioned. That is at most an administrative offense.

Tell me, do you sometimes drive 52 in the city instead of 50? :D

I'm certainly no saint, if that's what you mean.
An architect who suggests I break the building regulations because everyone does it fails my criteria.
Not because I find breaking building regulations "unforgivable," but because it makes me suspicious.
I choose my business partners. Nothing more, nothing less.

I think the building authorities are overrated in this regard, they approve and are glad to get rid of the building application.

Except for a few veterans, you only find civil engineers there who find nothing outside. The offices are all overloaded and suffer from staff shortages.

Why do the building authorities take drones? They should network with the [Ämtern für Bodenmanagement], which have very useful orthophotos of the entire state area and even staff who search these every day for topographic changes. If these officials were commissioned to also look for XY and, if necessary, report to Z, one would have plenty of cases in no time where one could go knock on doors. In fact, this is not done because there are more important things for the scarce staff.