Building on still foreign land - Waiting for building permit

Yes, for us it was about: Buyer acquires land on which a farmer still has a lease contract that could not be terminated prematurely. Solution: Buyer builds with our consent and compensates the farmer. We terminate the lease contract with proper notice. Buyer pays after the land is free. Buyer becomes owner now. Another possibility would have been: ownership transfer immediately with the lease agreement. But for various reasons, the buyer did not want that. - My example was ONLY meant to show: Building on land that does not yet belong to me is neither impossible nor unusual. Karsten

Eyeyey.
People.
Possession <--> Ownership.
Especially with real estate, these are two clearly distinct legal concepts.
The provision in the contract is clear and quite standard. Possession transfers upon payment of the purchase price. From then on, you can start building.
That ownership only transfers months later after the land register has been updated simply does not matter.
So, talk to the notary and the bank; it should be resolved quickly.