So from southern BaWü (also rural) I can realistically recommend 3000€nt for a good standard.
Additional areas (garage) are about 2000€nt.
Additional construction costs are a pig in a poke.
For us, about 60k€ were estimated and now we had to pay 38k€ just for fresh and wastewater. Our plot is located in an urban area!
These costs are really hard to estimate.
Our garage is about 54m2 and the shell construction alone is already about 70k€.
So you can easily calculate 100k€ including gates, plaster, sealing etc. etc.
Your project is very generous. That includes corresponding bathrooms, flush doors, wooden floors, good lighting, smart home!?, and suddenly a project like yours amounts to 1 million €.
We come out at about 915k€bt without land. 155m2 living area including the aforementioned garage.
No outdoor facility is currently planned.