Purchase of a building plot with traffic area

Isn't it the case that the city simply enters into the purchase contract? That is, buyer and seller notarized by the notary. Then the city decides whether to buy at the price agreed upon in the purchase contract. So it should neither result in less money for the seller nor higher costs for the buyer. Hopefully, the buyer will not have to cover the notary fees for the city. I can't explain what the seller objects to. Maybe ignorance of how the whole process works?

if the OP rats out the community,

Nobody has to rat anyone out. The community is informed after the purchase if it has a right of first refusal. Then it either steps in or issues a document stating that it does not want to buy. The notary then needs that.

The community is informed after purchase if they have a right of first refusal.

After the purchase? – then it would actually make a difference whether you told her that she should come to the appointment.

§ 28 Building Code - Procedure and Compensation
(1) The seller must immediately inform the municipality of the content of the purchase contract; the notification from the seller is replaced by the notification from the buyer. The land registry office may only enter the buyer as owner in the land register in purchase contracts if proof of non-exercise or non-existence of the right of pre-emption is provided. If a right of pre-emption does not exist or is not exercised, the municipality must issue a certificate to this effect immediately upon request of a party involved. The certificate is considered a waiver of the exercise of the right of pre-emption.

By the way, it also states that the municipality enters into the purchase contract with all rights, duties, and costs and must compensate at the stated price. Unless it is apparent that the purchase price is significantly above the market value. What counts as significant now probably leaves room for interpretation.

Isn't it the case that the city simply steps into the purchase contract? In other words, buyer and seller notarize the contract. Then the city decides whether to buy at the price agreed upon in the contract.

That's exactly how it works. The city steps into the notarized contract with the notarized price.

means after the notarized purchase appointment. But just before the land register entries. The notary has to obtain a certificate of no objection. This way, the city gets notified of the appointment anyway. However, I don’t know if this invalidates the entire purchase contract and if a new appointment with possibly additional costs is then required.