Level change and cost sharing in Hessen

a complete version of the HNRGs might be more enlightening

No, it is not, because it does not regulate anything in this regard. But querying a search engine provides the references for the full text.

I don’t want any quarrel or trouble... because something like that might never settle again.

That’s right.

But I am not willing to give everything away to others and then turn over every euro myself.

If your neighbor, who is rock-solid convinced of his statements, thinks the same way, it looks bad. You have to talk to each other kindly and openly, argue, and reliably put facts (including costs) on the table. The paragraph 909 of the German Civil Code, already quoted, will help you already.

ok...I just took a look here

That is good, even though it is not allowed to post links in this forum. The Hessian Neighbor Law does not help you with your current question, but you still have to agree on the enclosure and it certainly doesn't hurt to know the legal basis regarding this. If people were reasonable, it would be quite simple: Your neighbor must intercept their excavation according to Building Code 909. For this, they would have to come up with a technical solution that would cost them x euros. You must intercept your embankment according to Building Code 907, which costs you y euros. You should be able to substantiate your costs in a comprehensible way, e.g. with concrete offers or hardware store brochures and a realistic estimate of effort. Ideally, the total sum x+y is sufficient to intercept the entire height difference. If not, the additional costs are to be shared.

That is good, even though it is not allowed to post links here in the forum.

oh with... then that has to be removed, I can no longer change it

I can only hope for you that a logical approach must be taken here! So that your neighbor also has to pay. With us, it is regulated, everyone may make or support a maximum height difference of 60cm. A shared support (higher than 60cm) is not allowed.

It is regulated with us, everyone is allowed a maximum height difference of 60cm or to support up to that height. A shared support (higher than 60cm) is not allowed.

Does this mean that for you the maximum height difference is limited "to the neighbor" and not "to the original terrain"?

That means the maximum height difference is limited "to the neighbor" and not "to the original terrain"?

I would understand it this way that the maximum height difference here is limited to 60 cm per property. The neighbor could also adjust their 60 cm height, and you would come to a max of 1.20 m, then you would have two walls running side by side,

right?