Extension on an old building from 1965 with an additional storey

Thank you for the info. Could it be that this only works for cities or similar? Or where can I find that? Do you have an example of where I can find it?
Thank you very much in advance.

Open Bayernatlas, click on "Thema wechseln" in the menu on the left --> Plan and build --> click on Bebauungspläne Bayern --> search for your place --> yellow border means development plan. Usually it is stored when you click on it. We are also in an absolute village location and everything is included here (Marktgemeinde)

Edit: of course, it can also be that there is no development plan for your street and it is governed by neighborhood development §34

The neighborhood in old residential areas is always a good indicator of what might be possible for you: Are there already houses in the neighborhood that have been extended upwards? Are there already houses with flat roofs there?

Your questions cannot really be answered without knowing the house better. Please post floor plans and sections here.

3. Hat evtl jemand eine andere Idee, wie man es realisieren könnte?

Find and hire an architect.

Das Haus hat aktuel 1,5 Geschosse mit Keller
[..]
Aktuell befindet sich über dem OG ein Dachboden, der zwar in der Mitte etwa 2,5m hoch ist

But the 3D "sketch" does not look like that. Is the roof very steep?

Thanks again. Online I can't find a development plan, when I click on it, only a window appears: Object Information, no further information. But even in other randomly searched municipalities I find nothing. Either I am searching incorrectly or it only exists for a few municipalities or even only for new development areas. It is a mixed-use area with different buildings. Single-family house, multi-family house, industrial hall, etc. I will simply contact the municipality and then I will know.

With us (bw) there was also nothing online yet. However, the email came surprisingly quickly (within 24 hours).

Just tell me the Gemeinde/Flurstueck? Then we'll find it.