Garage at the border higher than 3 meters (Hessen)

Hello,

due to a hillside location, we would greatly benefit from a garage set at a higher level. We have already spoken with the neighbor, and 3.2 m would also be acceptable for him. Now the question arises: What needs to be arranged so that this solution can have permanent validity? I assume that a simple note between neighbors and us is not sufficient. Who has experience with this in Hessen or other federal states, or generally knows about this and can say whether a permit from the authorities, even if the neighbor agrees, is still complicated and costly?

Your neighbor will probably have to register a setback area easement on his property, and it will only be possible if he has not built anything directly on his boundary, as otherwise the setback area would not be provided.