Permissible wall height - what does that mean?

I want to buy a plot of land on a hillside. The street side is about 3 meters lower than the plot. Currently, there is a wall about 1.50 meters high directly at the street. The plot itself is relatively flat. I imagine building a house into the slope with a garage in the basement. Then I would like to build a ground floor and an upper floor (possibly with knee walls). A pitched roof slope of 38-45 degrees is required.

The development plan specifies a maximum wall height of 4.20 meters. Also the following explanation: The wall height is measured between the curb height of the access road at the level of the centroid of the building footprint (reference height) and the intersection of the outer wall with the upper edge of the roof covering. The height difference between the curb height of the access road at the level of the centroid and the terrain level at the centroid can be compensated by an increase in the permissible wall height up to the amount of the height difference.

Does the basement count towards the maximum wall height of 4.20 meters?

Can someone explain this addition to me and perhaps roughly assess whether the planned construction method is possible or what I should consider in my thoughts. Of course, I will consult an architect. Unfortunately, I have to decide relatively quickly for or against the plot and hope for help here.

Oh ... you again ... that's not exactly your first project either ... have you ever completed any of the previous ones or are they always stuck somewhere?

The development plan specifies a maximum wall height of 4.20 m.
Also the following explanation: The wall height is measured between the curb height of the access traffic area at the height of the centroid of the building footprint (reference height) and the intersection of the exterior wall with the upper edge of the roof covering.

Wall height means eaves height, so at the upper end up to where the roof (imagined as if it had no overhang) lies over the outer edge of the exterior wall. Curb probably means, in a traffic area without sidewalks, what would otherwise be called a kerb. The non-official person would probably simply call the traffic area a street in layman's terms. The lower end of the "wall height" measurement is taken at the upper edge of this curb; namely at the point where you meet the curb if you go there from the centroid of the building. This stupid formulation (instead of simply "house center") is in my opinion a legally untenable (because "not sufficiently determinate") ridiculous nonsense, a fool’s invention by some contrarian faction in the municipal council. Someone probably feared an unequal treatment of houses with L-shaped floor plans or asymmetrical bay windows compared to houses with rectangular floor plans, and what came out is highly amplified confusion for the citizens affected. Anyway, from there it should be a maximum of 4.20 m – which usually will be enough for a practical knee wall, if your ground floor is not far above the street.

The height difference between the curb height of the access traffic area at the centroid height and the ground level at the centroid can be offset by increasing the allowable wall height up to the amount of the height difference.
Does the basement count towards the maximum wall height of 4.20 m?

The clause that makes this nonsense even more incomprehensible probably means: if your "raw plot" (= before terrain modeling) is above the street, you are allowed to add the difference to the 4.20 m – why not just use a different reference height, the gods know. Amateur politicians!
Where your basement ceiling lies height-wise, you will probably have to figure that out yourself; so according to my reading: the above-ground part of the basement does count.
But this was written by a real enemy of the citizens; what kind of "lovable" dimwits do you have in the municipal council... their complexes could probably keep a whole association of psychiatrists busy ;-)

The street side is about 3 m lower than the property. Currently, there is a wall about 1.50 m high directly at the street. The property itself is relatively flat.

How should one imagine this? Is the slope at the street being supported by the wall? A section or picture would be helpful. Wall height is—simply put—the side of the wall visible up to the roof cut from the reference height. At 4.20, a one-story building plus a gable roof with about a 120 cm knee wall is possible if the cellar is buried. The building authority can explain more precisely by phone.

insufficiently defined

What? It’s explained quite well. Even with a drawing! Whoever doesn’t understand that ...

That is indeed the most convoluted formulation and explanation of a height determination I have ever come across.

But that was written by a real enemy of the citizens, what kind of "lovable" dimwits do you have on the municipal council

And this is not a one-off slip. They found the formulation so great that they used it in a whole series of development plans.

Does the basement count towards the maximum wall height of 4.20 m?

If you manage to determine the height of the centroid with the enlightening explanation for calculating it, the question could be answered. Suppose your also not exactly clear description of the property's topography results in your centroid being 2 m above the reference point on the curb, then your wall may be 6.20 m high. Whether there is still space for a knee wall with a basement garage is questionable.

A cross-section ... would be helpful.

I agree with that and would also wish for a site plan with a meaningful height grid.

What? It's explained really well. Even with a drawing!

Not just "well," but surpassing my worst fears about the kind of geometric prose bored council members are capable of. The faction leader was probably a math lecturer at an administrative academy. This is truly the most original method of determining flowing reference points I have encountered in four years of a house construction forum. One could actually make a tendering procedure for building plots out of this: whoever (first) calculates the correct reference height above sea level may buy the property; for up to three plots you may submit one calculation *ROTFL*

Thank you for the numerous responses.

Maybe this helps further. The question for me is whether an attic is even allowed and approximately up to which knee wall height.