Advance request for examination of building application / building permit

Well, I don't even know if it's good or bad. The only thing I know about the topic is that this fictional building permit takes effect after the 3-month period that the building authority has. But exactly when does this period start? From the date of the acknowledgment of receipt? From the day the application is checked for completeness? And how does it behave if the application would theoretically be rejected after the start of construction because, for example, boundaries were not adhered to or something else?

The confirmation of receipt should include a sentence that roughly says, your application dated, here received on..., date. From then on it counts. Anyone who does not want to be tricked should send it by registered mail. The three-month deadline is interrupted if the application cannot be processed because something is missing. Whether non-payment of the advance affects the deadline, I do not know exactly, as I am not familiar with such advances here. That would be legally interesting, whether an authority may demand money beforehand in order to fulfill its legal obligation, otherwise nothing happens.

But from exactly when does this deadline start? From the confirmation of receipt? From the day the application is checked for completeness?

One can probably request a certificate stating whether the fiction has occurred.

Basically, "slipping into the fiction" is generally, in my opinion, rather positive.

That would be legally interesting, whether an authority may charge money beforehand in order to fulfill its legal duty, otherwise it does nothing.

If it is stated in a statute, probably yes – however, a statute can also be incompatible with higher law. But that, I fear, is a matter for the specialist.