Interesting file. The question remains when the service is considered rendered? Actually only upon completion. So only when the last screw has been tightened.
It also says something about [Abschlagszahlungen]. But it sounds as if the final invoice would be decisive!?!?
Then the building acceptance should be decisive - service rendered, remaining balance becomes due. That’s how I understand the document with the example bathroom renovation. Oh, construction stop now, acceptance is at the end of June.