Land registry entry takes forever

Here it is questionable how this is regulated in the purchase contract. You write that you have already paid. If that is the case and the payment went directly to the seller, then I assume that the "handover" of the property has probably already taken place. When the handover is, that is also stated in the purchase contract. If it has taken place, then you are "immediate possessors" and could use the property without restrictions.

The nice thing about these purchase contracts is that the seller cannot just change their mind anymore.

In my opinion, you can therefore start with the measures and do not have to wait for the ownership status in the land register.

It all depends on the purchase contract.

I just looked at the purchase contract and as far as I understand, we are the owners from the day the purchase price is paid. Everything still has to go to the land registry office and be transferred, but that just seems like a formality.

What surprises me is the statement from the secretary (I called the notary this week) and she said: "Well, I wouldn't start building yet if I'm not registered in the land registry. For some reason, the purchase might still not go through. The sellers could change their minds and then there would be just the shell of the building. So I would wait."
That surprised me too, because we have already paid and for me, that is just a form of bureaucracy.

All of this confuses me :-(

I do not know the contract, but the fact that the notarial clerks are often remarkably clueless ... is no secret. ☺️