Plan the house first and only then buy the land?

Or let's ask it differently: What do you do with the place - assuming an unchanged(!?) lifestyle, what do you use all the square meters for?

A house, especially in that dimension, IS a lifestyle change per se. You might mean that your personality doesn't change?

@Biber0815 asked whether a down-to-earth house of normal size with some features wouldn't better suit the lifestyle
That would interest me too

It sounds as if you have lived moderately and saved all the time to now build a palace. On the one hand, I understand that, of course. For the saving, now I treat myself to something.

I just hope you won't be disappointed when the huge house stands there. You might find that you actually only use 4-5 rooms of the palace. The rest is more or less ballast that costs only energy and work.
I would think carefully about what I really need and what is also cozy.

I don't find the house as exaggerated in size as everyone here makes it out to be.
-Dining/living room maybe 50-60sqm, well somewhat bigger than standard
-Kitchen with small dining table nothing extraordinary
-Parents' area with dressing room and bathroom all our friends have that in their city villas and they built theirs much cheaper. No, I don't want it just because everyone has it. Then I would also want an open kitchen. But I don't want that.
-2 children's rooms 16sqm also not unusually large
-Office 14sqm also not particularly large
-Fitness room 30sqm ok not everyone has that
-Ok extra bathroom for the children and guest toilet but besides that, it's not a huge palace.
How do people come up with 4-5 rooms that I don't use every room is needed.

If you add that up, including [Haustechnik] and [Abstellraum], does it then come to 250 - 300 sqm?

I would have estimated 200 - 225 by now. That's not a small difference.

So with 250-300 I mean all rooms, storage rooms, hallways, heating room, etc.

So with 250-300 I mean all rooms, storage rooms, hallways, heating room, etc.

That's what everyone else means too, or do you think that in a 140 m² house the hallway and utility room are not included?

I already find it annoying to clean up our child's mess in 140 m²... I wonder how it would be in 230 m²...