Fencing in RLP: Is a small fence allowed on private property?

In my opinion, they are pretty expensive. And yes, if you have a somewhat larger stone in the way, the foundation screws around it. That wouldn’t be the worst thing with [Maschendraht], but if you want to install fence panels, it’s definitely annoying.

I didn't even know that cement and concrete are different things. Let alone that you can mix one from the other.^^

Yes, flour and cake are not the same :)

I don't see the advantage of the screw foundation. For solid ground, a driven sleeve should be sufficient for a fence, they are significantly cheaper and driving them in is probably less effort than screwing in.

Advantages: Screwing in is possible quietly. More adhesion. Theoretically greater depths possible. Does that justify the price? Not for me.

Although expensive, but as a newbie in DIY for a few posts:

Ruck-Zuck concrete is indeed expensive, but very practical to use. I would put a bag of it in every hole. Align the post (get a post level for a few euros at the same time) and pour it in (no need to mix beforehand) and the thing will stand upright to start with.

Then, depending on the desired strength, pour some cheap screed concrete (ready mix that now needs to be mixed to a damp consistency) afterwards.

With that, it really is no more rocket science. More expensive than mixing cement and sand yourself, but fast and well suited for DIY. You only need a string and a few string irons and you will have a proper result.