Leveling the plot with Berliner formwork with steel infill

I want to purchase a plot of approximately 468sqm for building a single-family house. The rear part is to be used as a garden. However, the rear approximately 10m over a width of about 16m slopes steeply (maximum height difference about 2.5m). At the end of the plot there is a stream that is part of a nature reserve. The neighboring properties have not equalized the slope but have instead planted grass or created terrace levels/steps. For me, a purchase only makes sense if I can level the rear part. An acquaintance from the construction industry gives me the following recommendation: Berliner retaining wall with steel infill, greening the wall on the sides facing the neighbors. 1) Is this technically feasible? 2) Are approximate costs of €25,000 realistic? 3) Is a permit conceivable? 4) With which authority should I clarify the permit before the purchase? Thanks in advance for any tips!

1) Is that technically feasible?

Sure, that’s exactly what the retaining wall as a Berliner retaining structure is intended for.

2) Are approximate costs of 25,000 € realistic?

No, never, worst case six digits, since the retaining wall could be complicated to found in a stream bed.

3) Is a permit conceivable? 4) With which authority should I clarify the permit before purchase?

Presumably, everyone has a say here: the lower water authority, environmental office, city, etc., etc.

The biggest problem will be: You intervene in flood protection by narrowing the potential flood channel instead of flooding your back garden. You might be destroying a designated floodplain (a red trigger word for any approval procedure), etc., etc.

Your long-established neighbors will be quite jealous because then you would have a great property, and that’s the beginning of the end anyway.

Only the Berliner Verbau or a concrete wall.
The Berliner Verbau will eventually rot.
I find the 25,000 euros too low for the reasons listed by Mottenhausen.
You also need a fence on top, so no one falls over the wall in the back.

Check with the building authority. They can tell you if it would be approved.

Don’t forget, the whole thing still needs to be filled in. That involves quite a few cubic meters of soil, excavator hours, truck trips, and compaction times.

Thank you very much for the very helpful assessments. I will contact the authority by phone.