Selling new construction after receiving funding / Wohnriester - possible?

Not really, no. But I don’t want to look for the next annoying neighbor. I’m rather searching (for a needle in a haystack) for a standalone property, an old farmhouse, a bit further out, without immediate neighbors, with a lot of land of its own. Then no one can disturb you from the side, if no one’s there. I don’t find it so far-fetched to consider it a major factor in quality of life if you can sit in a quiet garden after work and listen to leaves and birds. If that’s a crazy wish, then I’m just crazy. :p And that’s why I actually just wanted to gather experiences here, whether anyone has ever done it, selling a new build and buying/ building anew elsewhere. There can be many reasons for that, it doesn’t always have to be the neighborhood.

Wouldn’t it be more obvious, before such an extreme, probably financially rather tricky step, to tackle the underlying problem and maybe see a psychologist? It really does sound more like "pathological" when you listen to your descriptions. Maybe talking to a psychologist would make sense – to me, it all sounds like the condition called Misophonia. Many people have it, for example with smacking noises, but it comes in countless forms and is treatable. In my view, it’s definitely worth a try.

I wouldn't necessarily call that pathological. However, I also don't understand the self-evidence why suddenly owning your own house means you no longer have to be considerate. I would never have thought of listening to music in the garden in front of our neighbors' houses. I don't have to impose my taste in music on anyone, especially not so loudly or bashful that it can be heard inside the house. That is inconsiderate and unnecessarily provokes. So much so that it even disturbs at a relatively low volume. I only do it so I don't have to continuously listen to the chatter on the phone's speaker. Besides, I find that inconsiderate too; I listen to these calls for hours and hear both of them talking. If I knew the language, I could join in.

We once had a user who sold again 1-2 years after the construction. I believe the property was located next to a noise barrier, the exposure was higher in everyday life than expected. Maybe someone will look there sometime (or uses his elephant memory)

I would first properly talk to the neighbor. Not over the garden fence, but sit down calmly. Make it clear to him how much it bothers you, that it makes you sick. And then maybe find a compromise, fixed times and the limitation to a few hours daily, for example. Then at least for the time until you find something suitable, you will have some peace.

After therapy has been suggested to me repeatedly now: I was in therapy for many years and talked about many things. For the most part, this resulted in a massive improvement in my quality of life. I am the last person who would advise someone against therapy. On the contrary, I believe I can count on one hand the number of people in my circle of acquaintances who wouldn’t need it.
One insight from therapy was also that you are not always broken when you are different. Many people like to believe that – they are welcome to see a therapist then. But you don’t always have to see the fault in yourself, and not every personal trait is a psychological defect.
Regarding the mentioned "Misophonia" pre-diagnosis: I briefly looked it up on Wikipedia – the word "music" does not appear anywhere in the article. It’s about various sounds one can develop hatred for (I have also seen a TV report about this), but music is not mentioned among them. I also believe it is not uncommon to develop hatred toward people who bombard you with unwanted music. In my case (and this also speaks for a personal trait, not a psychological disorder) I generally find music exhausting. I don’t listen to music constantly in the background privately either; I don’t like annoying noise in general. Even when I cause the music myself (have it on), I can’t keep it on when I start doing something else that requires concentration, like playing a game. Music for me is something active, something where I am engaged.
Recently, we wanted to eat on the terrace behind the house on a Sunday because the weather was nice, and again there was annoying noise coming from the neighbor. And I found it difficult to talk to my husband. I can only listen to him properly with great effort because my attention keeps landing on the rhythm. It’s like two people pulling your arms in different directions, metaphorically speaking. I can’t split myself. I can’t explain it any better.

Try to switch your mindset. You are already charged and focusing on the music before you hear it.

There is no peace even in the middle of nowhere.
Birds at 4:30 are not exactly quiet
Tractors even on weekends, especially now during harvest time from sunrise to sunset
In good weather, the forest paths and the corresponding access roads overflow with walkers and dogs.
Oh, and don’t be startled if a cow suddenly appears in your garden. For some cows, electric fences are an annoying gimmick by the farmers, but not an obstacle.