Plot with terrain drop - separating wall neighbors - foundation?

Unfortunately, after the excavation, the neighbor has already backfilled a large part again and is cheerfully using our construction water for concreting. Here are some photos for you - I am curious about your opinions!

And here are three more. In the last picture, you can see that there is about 8 cm of space between the wall and the garage; behind it is a water pipe. So the wall will not contribute to the stability of the garage later on.

in the last picture you can see that there is about 8cm of space between the wall and the garage, behind which there is a water pipe. So the wall will not contribute to the stability of the garage later on.

Regarding the garage, I still don’t see anything that convinces me of good long-term stability. Otherwise, the wall is just as I had imagined it from your textual descriptions: the neighbor has basically made "L-stones according to his own recipe." From a construction engineering perspective, that’s not foolish or naive, even if unconventional from an official point of view. You can certainly do it that way. Not "usual," but still looks neat. With Rhenish composure, we could almost just put a stamp on it.

Regarding the garage, I still don't see anything that convinces me of good lasting stability. Otherwise, the wall is just as I had already imagined it from your textual descriptions: the neighbor has basically made "L-stones according to his own recipe." That's not stupid or naive from a construction-technical standpoint, even if unconventional from the perspective of official German bureaucracy. You can certainly do it that way. Not "usual", but still looks neat. With Rhenish calmness, we could easily put a stamp on it.

Uh, don't get me wrong – but these L-shaped stones are on his side. How are they supposed to counteract the earth pressure towards me? Or am I misunderstanding something?

What about frost protection and drainage? Meanwhile, I've watched several "foundation tutorials" online, which always talk about at least a 30cm gravel layer plus drainage for a foundation at least 80cm deep like this one:

What I see in the pictures tells me that this could hold. He has already thought about anchoring in the ground through the anchored brackets. Poles on the construction site? Or? It's really not that naive. And he apparently uses enough concrete as well. Karsten

Thanks for the info! At least somewhat reassuring! He had started these extensions in his garden on Thursday, after our site manager had expressed serious concerns again. I still don’t quite understand why this benefits him – could you please explain that to me? We were told that a clean solution with L-shaped angle plates is possible, whereby the L part would have to be below our lawn due to the approximately 45° terrain pressure, so that support effect occurs here.

How should the whole thing be assessed in terms of frost protection and drainage?