Leak test passed but water is leaking out

And now again:

Which contracts exist with whom?

Did you arrange the inspection? Or your construction company? Is there even one? Or single trade assignment? So many questions....

And now again:

Which contracts exist with whom?

Did you initiate the inspection? Or your construction company? Is there even one? Or single-trade contracting? So many questions....

Yes, we made the contract with a civil engineering company who did the civil engineering for our house and connected the outside drainage to the sewer. They referred us to this leak-tightness testing company. Therefore, the civil engineering company should be our contact person.

Do you have everything from a single source or a separate contract with the [Dichtheitsprüfungsfirma]?

The easiest way will be to have both parties involved, who are blaming each other, come together.

Hello

What exactly was the "Dichtheitsprüfung" (leakage test) carried out for? Rainwater drain? Wastewater drain? And where is it leaking?
What is the causality from the drain to the wet screed?
And how can one pierce a cable of the bus system when drilling a hole in the screed?
First of all, there are many questions of understanding to clarify.

Steven