Otherwise, I also had a lawyer examine this issue with the lower-lying property: no chance of achieving anything here either, as liability for material defects is excluded in the contract – well... ancient history.
No, in my opinion rather nonsense from Holland. A material defect would have been if the property had suffered from a private seller that the development was done "on the surface." But here something quite different is the case, which I would rather call a "permanent trespass": the municipality is dumping a road in front of the property (by the way: to an extent that, in my opinion, constitutes a terrain alteration requiring approval and, since it is not sloped off there, also neighbor consent); furthermore, here the
injurer is in personal union the property seller. That means the seller was not only aware of the impending disadvantage, he even caused it himself and very likely intentionally (because the purpose of cost saving supposedly justifies the means).
No deterioration that happened, but a caused damage. From here I see it clearly without glasses that your lawyer is not "Liebling Kreuzberg." At least his friend, the procedural fox Dr. Wolter, would have taught the municipality a lesson here.