We are currently building, but not in Bavaria, rather in SH. The prices mentioned I also find very high. Regarding the wall. Please without Styrofoam, no thermal insulation composite system. So double-layered clinker with mineral wool in the air gap, unusual for you, right, or Ytong plus plaster. Thick Ytong. It can also be Porit or similar. That's how we build. It goes quickly, is ecologically okay, warm wall, little moss-prone, stable enough to bang a bicycle against it. To save costs, a more angular floor plan without many frills, always 110 cm FF windows, all the same, underfloor heating with gas and solar thermal, no other error-prone control technology, on the roof Braas double S silk matte, which also does not moss so quickly. Kitchen, ours costs 3500 plus 1000,- assembly, Ikea. You are welcome to buy windows and exterior doors at, for example, Grandpol near Stettin, good quality, fair price. We do nothing ourselves and thus come to about 1500,- per sqm without land, without outdoor facilities, with 135 sqm base plate floor area. So, with family support, if it really comes, just go ahead. Money is cheap. And always remember, keep it simple.