Height reference point boundary construction Brandenburg

Hello everyone,
I hope someone here can help me with my question. I can’t get any further with the search here or the search engine.
We are planning a garage as a boundary construction on our property in a fairly newly developed residential area. The building height of the garage may therefore be max. 3m. But what do the 3m refer to?
No explicit height reference point is specified/named in the development plan. Only individual height measurement points of the terrain on the properties are listed, as well as the height of the top edge of the future street in the area.
The street is supposed to be at height 78.10m. Our house has a top edge of the finished floor at 78.50m, since we had planned the driveway from the house towards the street with a slight slope and also planned a 1-2 step-high entrance platform in front of the house.
When planning the garage, the following came up:
If we want to use the max. 3m height, the top edge of the floor is only at 77.93m, since this is the height measurement point of the terrain at this point of our property. Thus, the garage would be below street level and 60cm lower than the house. The driveway would then slope towards the garage, and we would need a “proper” entrance staircase. Our architect says there is no other solution regarding the garage except either to do without the boundary construction or to reduce the height of the garage – both are not real options for us.
Is the architect right regarding the height reference point? It doesn’t make much sense in terms of planning on the part of the city, as the height of the street at 78.10m is higher than all the terrain height points in the building area on the developed properties.
Thanks in advance for the help!

How are we supposed to know what is in your [Bebauungsplan]?

"In der Regel" the information refers to the natural ground level.

Option 1: Ask the building authority Option 2: Talk to the neighbor. If they have the same problem, you can often reach an agreement easily.

If the street is higher, is there then a slope in the terrain?

Show us the site plan with the elevations.

The building height of the garage may therefore be a maximum of 3m. But what exactly do the 3m refer to?
No explicit height reference point is specified/named in the development plan.

That would at least be unusual if the development plan spoke of the building height here; the given measure is usually the limitation of the average wall height, and the reference point for the building height is not relevant here. For details, I can only recommend the posts by .

Only individual elevation points of the terrain on the plots are listed, as well as the height of the upper edge of the future road in the area. The road is to be at an elevation of 78.10m. Our house has an upper edge of finished floor level of 78.50m,

These elevation points describe the original terrain relevant solely for your question. Your apartment floor level is not of interest here: the wish of many builders for a level passage between garage and house is not a protected concern in terms of building law - but often an unavoidable point of compromise.

Option 2: talk to the neighbor. If they have the same problem, it is often easy to reach an agreement.

The neighbors may be in the same boat with the problem, but they cannot effectively exempt each other from the regulations themselves. They can only express to the building authority that they do not oppose a request for exemption.