Living space effectively approx. 180m²
very roughly and please also search for costs here in the forum:
180 m² x 1800 Euro/m² = 324,000 Euro (really cheap from 1400 €/m², no upper limit, those who build big do not want cheap).
Basement 40,000 Euro (rather more)
Double garage 30,000 Euro (with the roof and outhouse gladly more)
Additional construction costs 30,000 Euro (gladly more)
Construction supervision, expenses, miscellaneous .... 10,000 Euro (???)
All in all: 434,000 Euro. Plus unforeseen costs. Plus special requests, plus outdoor facilities (paved areas, fence, garden).
The biggest saving potential lies in the living space, the second point in my opinion is the garage complex (cf. precast concrete garage on strip foundation).
Everything that can be said about the floor plan has been said ...