Single-family house with basement in Upper Franconia

Hello everyone,
we are also slowly entering the planning phase since a new development area is being built in the hometown of my partner and we have already reserved a plot there.
Of course, we have already put our heads together and thought things through, and before we sit down with a planner, we want to see if our wishes are still within a reasonable range.
About our project:

[*]Plot 649 sqm x approx. 100 EUR (developed) = 70,000 EUR including acquisition incidental costs
à still undeveloped – will be developed by the municipality (100 EUR planning price from the mayor)

[*]Elevation difference approx. 80 cm

[*]Located in Upper Franconia, Bavaria approx. 15 km north of Bamberg, rather rural
[*]Freely designed detached house in solid construction (approx. 11 x 9 m)
[*]KfW55 standard or better, if possible
[*]Gable roof 20-25° or possibly shed roof
[*]Approx. 150 – 160 sqm living space over 2 full floors (high knee wall)
[*]Standard basement; clear room height ground floor and upper floor 2.65 m
[*]Landing stairs
[*]Relatively open floor plan with 1 bay window (approx. 4 x 1 m – for the partner’s aesthetic reasons)
[*]Windows in aluminum, several patio doors on the ground floor, standard sizes upstairs, all with electric roller shutters (possibly as smart home)
[*]Ground floor + attic 85% vinyl, rest tiles (baths, hallway), standard tiles in basement
[*]Underfloor heating + fireplace with Swedish stove
[*]Central ventilation system with heat recovery
[*]Air-water heat pump for heating, possibly with hot water system
[*]Basement as room reserve (laundry room with WC + shower, storage/workshop, party/recreation room, technology)
[*]Ground floor: study, guest WC with shower, dressing room, kitchen (semi-open), dining area, living room
[*]Upper floor: bathroom, 2 children's rooms, bathroom, master bedroom with dressing room
[*]Adjacent to the house there shall be a double garage approx. 6.5 x 7.5 m (including small bicycle and utility room) as well as a terrace

We will probably assign the trades ourselves, but also have an offer from a general contractor drawn up once.
Both our parents built their houses by themselves in owner-managed construction, and my father-in-law even built his completely by himself – so construction know-how is definitely available. Furthermore, we have various professions in the family or close circle of friends (drywallers, painters, window specialists, sanitary), so we hope for support here :-)! We also have a draftsman among our acquaintances. The father-in-law also works for a civil engineering and road construction company in the region, so he can carry out the groundwork himself.
We would now like to know in which price ranges we will probably move and where we might have to cut costs.
It would be great if we could get some assessments from you regarding prices and optimization possibilities so that we can further advance our planning :)!
Thanks in advance :)!

Nobody :-(?

I cannot tell you anything about the prices in Bamberg. But about the budget cuts, yes. Wall. Ytong 36.5 plus plaster is enough for KfW 55 and is the cheapest due to labor costs. It is a perfectly healthy, decent building material. Aluminum windows are, in my opinion, a gimmick. Why? Plastic, Poland. The biggest manufacturer is Drutex near Gdansk, who has outfitted countless buildings, including multi-family houses, cheaply. Drutex is also quite affordable. Why the roller shutters in rural areas? Garage in concrete, prefabricated garage. For example, Rekers. All windows in 110. This results in an interior window size that fits standard blinds from Ikea and so on. Also the kitchen. Our experience is, unbeatable price-performance. Kitchen studios are robbers. First they quote you a 10,000 euro kitchen, then they wave a deal, only today, if you sign now, they’ll give you the dishwasher for free, if you’re still not soft, the obligatory call to the boss follows, who gives another 10%. Then you’re at 8,500 and get the same as at Ikea for 5,000. Interior doors smooth. No smart home. No KNX. Luckily, not necessary. With a 25-degree roof pitch, normal concrete roof tiles from Braas or similar work. Little paving, lots of gravel. Why a cellar? What’s in the cellar can also go to bulky waste. You have to be able to part with things. Since hopefully no war breaks out between Bavaria and Prussia, excessive stockpiling is not necessary. So, that was some budgeting already. That can save you a good 30,000...