Filling in the garden vs. maintaining ground level

The following can be derived from our development plan regarding the terrain height:
Fillings to create a new terrain height are permitted up to the average height level of the boundary between the public traffic area and the building plot.

The approval of our building notification includes the following note:
The natural terrain level must be maintained.

The construction project is located in Brandenburg. Our property slopes down by 1 meter over 45m at the back. We would like to distribute the excavated topsoil of about 125m³ on the property and thus raise the terrain height in the garden behind the house by, for example, 20-25cm.

How should the note from the building authority be understood? Does maintaining the terrain level mean that it should remain roughly level or gently sloping?

Maintaining the ground level means not changing the heights. However, your planned change corresponds only to the subsidence depth of a loaded truck or the height of a generous stair step. And as you describe the property situation, the change would not contradict the stipulations of the [B-Plan]. If you answer "yes" to the following questions, you should consult the person responsible at the building authority: - Am I concerned with maximum safety? - Does the site plan for the building application include existing and planned heights? - Is the transition to the neighboring properties problematic?