Selling new construction after receiving funding / Wohnriester - possible?

So he is definitely on board. I know it bothers him less intensely than me, but we are a team and he wouldn’t want to maintain a situation that wears me down as much as the current one.

It is also the only practical solution for you. Look for something bigger with significantly more distance to the neighbors. You have tried it with more proximity and it obviously doesn’t work. In your situation, it wouldn’t be that important to me whether I come out at +/- 0 or make a 40k loss. You both aren’t “poor people” now, meaning both academics with financially lucrative fields (IT, right?). That at least makes it bearable in that regard. It also doesn’t help you if you don’t make a loss now but have to go into inpatient treatment in a few months because of severe depression. One can’t balance one’s mental well-being with money. Therefore, better to be as poor as a church mouse but happy in a fixer-upper with 1500sqm of land than unhappy in your new-build palace on a small plot. Of course, there is no new-build palace on >1000sqm of land for you, but rather an older house that still needs some work here and there. From what I read now, giving up is definitely the lesser evil.

That is a fact.

The repetition alone does not make it valid law or a fact.
So where exactly does it say that music in the garden affecting the neighbor is an undisputed fact? That is possibly your wish or your idea, nothing more.
There are also definitions of the term "room volume," but one could infer something from the term "ROOM...." alone, otherwise it would probably be called neighborhood volume.
There are countless, including highest court decisions on this subject, which have clearly ruled in favor of those seeking peace; nevertheless, I would not engage in such a legal dispute, and in the end, you can also be unlucky in court or end up with a poisoned neighborhood anyway.

For example:
Whether the listening is involuntary or voluntary, whether “radio droning” or an understandable transmission – the character of a radio inevitably leads to significant impairment. According to the judges' opinion, listening to the radio in a quiet residential area does not count as usual property use. The defendant was therefore ordered to immediately cease his noisy broadcasting.
Case No.: OLG Munich 25 U 1838/91. The Federal Court of Justice has also sided on the quiet side on several occasions.

I still cannot understand that I disturb someone with my music outdoors and yet continue doing it. For me, it quickly becomes clear WHERE or with WHOM the damage exists. I have to explain myself or be diagnosed as stupid because I like having peace. The comparisons with the fire brigade festival or lawn mowing deliberately miss the point, because it is not about that, but about ignorance, thoughtlessness, and lack of empathy.
Those who want to portray as an oddball are usually the first to call the police or lose it when the neighbor does something they don’t like. Writing about it here is probably easy and casual – but in real life, it looks different. I always read only about rights, rarely about duties. For example, there is the general duty of consideration, and why doesn’t the neighbor just put earplugs in for the music?
It is like in the past on the morning train. Everyone is tired and it is nice and quiet, and then some fool comes with headphones and you are annoyed by their clanging external noise.
This problem certainly cannot be solved by measurements and evidence, probably not really by walls either.

Google for Braun & Würfele sound insulation reflective, or noise protection in the garden, my beautiful garden.

Man man man... Always these people with the internet eggs... Well-intentioned advice is primarily one thing: well-intentioned. However, it is not helpful in this particular case. Kati knows where the problem lies and that it personally triggers her. She is looking for solutions and has asked a concrete question. And then the psychologists come out of hiding. Luckily, it is no problem to diagnose illnesses when you have read a few diagnostic reports. The lengthy studies are therefore unnecessary. And with the typical German babble, I feel like throwing up. Please turn it around and then consider how it sounds... Typically Turkish, that the new neighbors of oriental descent are constantly loud, don’t discipline their children, and all the women have to wear headscarves. my advice to you (as at the beginning here as well): You have considered many things when buying the house, unfortunately not loud neighbors. This bothers you personally so much that you are having health problems. I also consider a lengthy legal dispute with uncertain outcome, or the possibility of soundproofing, to be the second-best solution. Your quality of life should be worth a possible monetary loss to you. Look out for a property with plenty of space around it, buy it, and make another family happy with your house. How long do you want to remain in this unhappy situation for you? In my experience, it is not worth it.

my advice to you (as at the beginning here as well): You have considered many things when buying the house, unfortunately not noisy neighbors. That bothers you so much personally that you are getting health problems. I also consider a lengthy legal dispute with uncertain outcome, or the possibility of soundproofing, as the second-best solution. Your quality of life should be worth a possible monetary loss to you. Keep an eye out for a property with lots of space around it, buy it, and make another family happy with your house. How long do you want to stay in this unhappy situation for you? In my experience, it’s not worth it.

Thank you. I probably have to stay a while longer, the luck and misfortune at the same time: I have only recently accepted a new job. What is supposed to bring us a significant financial relief will be our downfall when it comes to changing property. I will first have to wait for the probation period before I can negotiate with a bank. Or does that not apply if you already have a mortgage running? Has anyone had experience with this?

I would start looking first. Or are there many properties with your criteria? If you are moving away from the area, you will need a new job anyway? Yes, it is rocky and complicated.