Mold on wood/ shell construction, is it possible to deduct the advance payment invoice?

You should get an external expert involved with such an investment anyway. For example, check out the Bauherren-Schutzbund.

Thanks for the tip.
The total investment is by the way 460,000 euros.

What is the total house price?

Either way, the €145,000 for the service you described is, in my opinion, already very bold. Especially given the condition.

Have you had the payment plan checked?

Thanks for the tip. The total investment is 460,000 euros, by the way.

Is the land already included in that?

If not, that seems way too high to me.

Payment plan is in 7 steps.

30 %
33 %
6.3 %
7 %
9.1 %
8.4 %
5.6 %

Otherwise, everything is actually perfect.. except for this mold infestation in the hatch. I have now found an expert near me through [Bauherren-Schutzbund] and will contact him on Monday.. he is just 3 towns away..

Is the property already included in that?

If not, that seems way too high to me.

Did I write before that the property is already included

416 sqm at 350 euros .. standard for our region

I stand by my position. With the payment plan, you are paying almost 50% of the house price for an unfinished shell without windows and interior walls. Unfortunately, this is anything but a coherent payment plan.

Regarding the defects, I cannot contribute much professionally at this point. At least, I would not accept it without prior approval from someone who knows their stuff.