Register a mortgage for property sellers as security?

Hello everyone!
Yesterday we received the draft of the purchase contract for a plot of land.
We want to buy this directly from the municipality.

The contract was drawn up by the municipality's notary!

The contract stipulates that we must live on the property ourselves for at least 5 years (which I can understand to some extent...) and otherwise pay a contractual penalty of €30,000.
This is to be registered as an interest-free mortgage in the land register!

Is this common practice?

I have attached the text passages...

Then not only the Sparkasse and the KFW would be registered in the land register, but also the municipality...

What do you think about this?

I would be very happy to receive some opinions.

Don't know if it's common practice, but if so, please put it subordinated behind the bank

and that behind the "Grundstücks-Grundschuld" & "Neubau-Grundschuld," otherwise you'll have a problem with the banks. They are reluctant to go subordinated and/or you'll get worse conditions

Does not occur frequently, but it is common (Sicherungshypothek is also subordinate, therefore harmless for your financing).

Do WE have the authority to determine that the mortgage is registered AFTER the bank?

What happens after the 5 years have passed? Can I then have the entry deleted?

Do WE have the authority to decide that the mortgage is registered BEHIND the bank?

It is already stated in the clause of the purchase contract you posted that your own land charge remains in priority up to an amount of XXX.

What happens after the 5 years have passed? Can I then have the entry deleted?

That should also be stated in the contract, that you receive a right to deletion after 5 years.