Terrace wall to the neighbor - What should we consider?

You can just say yes and amen to everything with you and let the neighbor do whatever he wants,

You call it "drama" when your neighbor doesn't want the same wall finish after he has compromised on the building height for you. You also want to dictate his barbecue area and build a fence that is 60cm higher than he wishes. Since he does not say yes and amen to everything, you insult him in a public forum. That is a no-go. You seem to have completely lost any sense of proportionality. This really has nothing to do with saying yes and amen to everything.

I want to have my own fence, 180 is enough,

Did I understand correctly, I don't have to fence in? The neighbor is not affected by us, or are we obligated?

Yes, so what now? Do you want a fence or not, if you don’t have to?! I think you have small children, so you would put up a fence! You can both put up a fence on the boundary, one like this, the other like that. I’m also just writing on my phone but can think clearly enough so that you can read what I write. The last posts and thoughts are probably directed more at your husband, who no longer listens to you?

Yes, so what now? Do you want a fence or not, if you don’t have to?!
I think you have small children, so you’d probably put up a fence!
You both can put up a fence on the border, one like this, the other like that. Whether that makes sense?!
By the way, I also write only on my phone, but I can think clearly so that you can read what I write.
The last posts and thoughts are probably rather directed at your husband, who no longer listens to you?

I want to understand the legal situation, what I must and what I may do. Of course, I want to build a fence, as I have written several times now. 180 tall on my property at the border. The neighbor is in a hurry, we only want to build next year. I do not insist that he builds on his side, he can gladly leave it. I just don’t want him to build 120 on his side and then we are not allowed 180 on our side because double fencing is not permitted.

You call it a "drama" when your neighbor doesn’t want the same wall finish after he accommodated you regarding the building height. Furthermore, you want to tell him how he should arrange his barbecue area and build a fence that is 60cm higher than he wants. Since he doesn’t say "yes and amen" to everything, you insult him in a public forum. That is a no-go.
You seem to have lost any sense of proportionality.
This really has nothing to do with saying "yes and amen" to everything.

What does your post bring now? I don’t want to have to justify myself, I can do without your personal attacks. When did I tell someone how to arrange a barbecue area?
You are allowed to build up to 2m on the border, I agreed with him on 186, he then only wanted 180, then the war started because we insisted on our 186. It was no real concession. He built the foundation without our consent on our property, we then tolerated it and built on it, of course, paid for it afterwards. Why shouldn’t I insist on a reasonably normal privacy screen, for which I am willing to build it on my property and at my expense? It is completely legitimate. I will no longer respond to any personal attacks. You may gladly refrain from your comments or ignore this thread. As you wish.

Ask him, 180 instead of 120 on the border, then you pay everything and it is yours.
Given how Mr. Müller is, he will probably be happy about the "bargain"
GD

I am still waiting because the neighbor on the other side also wants 180 and definitely doesn’t want to build lower since he is also annoyed by Mr. Müller and wants to sit quietly in the garden with children. Let them fight first, about the fence I want to make sure first what I am really allowed to do, then I will see what the neighbor wants, he also changes his mind every few minutes. If he is ready for 180, I will still offer it to him as you write, so that I have consistency. But he wants it uniform too, I don’t know how he will decide.

You call it "drama" when your neighbor doesn't want the same wall finish after he has made a concession to you regarding the building height. On top of that, you want to dictate his barbecue area and build a fence that is 60cm higher than he wants. Since he doesn’t say "yes and amen" to everything, you insult him in a public forum. That is a no-go.
You seem to have lost all sense of proportion.
This really has nothing to do with saying "yes and amen" to everything.

What does your post bring now? I don’t want to have to justify myself, I can do without your personal attacks. How exactly did I dictate anyone’s barbecue area?
He supposedly made a concession on the building height? You are allowed to build up to 2m on the boundary, I agreed with him on 186cm, then he only wanted 180cm, then the fight started because we insisted on our 186cm. It’s not a real concession... He built the foundation on our property without our consent, we then tolerated it and built on it, of course also paid retroactively. WHY shouldn’t I insist on a proportionate normal privacy screen, for which I am willing to build it on my property and at my own expense. It is completely legitimate. I will no longer respond to any personal attacks. You may gladly refrain from your comments or ignore this thread. As you wish.

Just ask him, 180 instead of 120 at the border, you pay for everything and it’s yours.
Given how Mr. Müller is tuned, he might be happy about the "bargain"
GD

I’m still waiting because the neighbor on the other side also wants 180 and definitely doesn’t want to build below that, since he’s also annoyed by Mr. Müller and wants to sit quietly in the garden with children. Let them fight it out first; regarding the fence, I want to first secure what I’m really allowed to do, then I’ll see what the neighbor wants—he also changes his mind every few minutes. If he’s ready for 180, I’ll still offer it to him, as you wrote, so that I have consistency. But he wants it consistent too; I don’t know how he will decide.

Question again, is that possible?

Let's start with the fence on the boundary. Your neighbor can require it as a customary enclosure and you have to contribute 50% of the costs. If you do not agree on a fence, you only have to pay the costs (50%) of the customary local enclosure. Besides that, there is another fence behind the shared enclosure. That is also possible, but you should keep some distance from the fence on the boundary. Also, the fence must not harass the neighbor or be an "unreasonable impairment." So, a 2m high concrete wall as a fence would probably have to be torn down upon request. A normal fence (double bar panel etc.) at e.g. 50cm distance is allowed up to 2m height. Limitation: Check the development plan, as it may contain regulations deviating from neighborhood law.