Documents are missing for the first partial payment

The risk always lies with the builder. The financing commitment is always tied to conditions. And bureaucratic delays etc. are somewhat unpredictable. You have to consider that yourself. There are builders where the construction is delayed because the building permit takes 1/2 a year instead of 3 months, and interest then accrues. But it is the risk of the builder who signs the contracts along with the conditions.

.. why should I pay "penalty interest" if the developer/notary fails to obtain the documents and submit them on time?

Because that is simply your problem and not the bank’s. You could have also arranged the financing differently. That is just normal life.

The notary hardly cares that you need money. The hardest part of building our house so far has been that the notary does his job. Our land charge could only be registered last week after three months because the notary works too slowly. Fortunately, we were still able to scrape together money from equity to pay for the shell construction (interior finishing is underway). I wish you lots of patience. Please don’t waste your time and nerves thinking about who you can sue. It’s no use.

I had a list from the bank of what was still needed. I called every day to follow up until specific documents were there. We even handled the transport of a document, picked it up and delivered it (Notar -> Gericht), I think that was during the sale, with other documents we kept following up by phone.

What on earth possessed you to start new construction without taking a 3-month provision-free period? Just because the base plate is in place? Really, every information site available online advises taking at least 12 months!

Regarding your question, if the construction period is not exceeded, no one has to pay you anything. So, your own fault.

3 months are taken when purchasing immediately available stock objects, otherwise not.

Unfortunately, you miscalculated.

Besides, I don't understand why you see the notary as the culprit. He clearly responded that he cannot register the land charge due to the lack of the certificate of exclusivity. Without this, the land register sheets for the individual apartments do not yet exist. The building supervisory authority issues the certificate of exclusivity upon application by the builder.