Single-family house approx. 180 m² - What do you think about that?

:for us it's the other way around, behind it is a utility room with 11sqm, I would have preferred a guest toilet that is 10-20cm wider. But hindsight is always 20/20, so my advice is to build wider than 1.20. The length for us is 2.50 with a window

Good morning and thank you for the many responses.

Regarding the WC issue: in our rental apartment we currently have 1.35 x 1.65. Both the WC and the sink are located on the right side when viewed from the door. We find that quite spacious. We have also visited several houses where the WC was 1.2 m wide, with the WC located at the back. We think that is also very acceptable. Maybe 5 cm more in width, but that works for us.

Regarding the orientation, the location of the wellness area and our habits: we really only use the bedroom for sleeping, so we would prefer the orientation to the east to avoid letting heat, especially from the west, into the bedroom.
In the living room, we are mainly there in the afternoons and evenings during the week, so we prefer the orientation to the south or west (in this case west), although we also see that this area is too small in the current plan.
I think the wellness area in the south has the following advantages: as you said, the sauna is rarely used in summer but all the more in winter, especially on weekends and also during the day. I believe the wellness area in the south is ideal to be able to enjoy the sun as well. During the week in winter it will not matter since it gets dark early anyway.

Regarding the toilet topic: in our rental apartment we currently have 1.35 x 1.65. Both the toilet and the sink are located on the right side as seen from the door. We find that quite spacious.

No way! Since when is 2 sqm spacious?? I am quite slim but even for me 2 sqm is far too little. Surely there are also 1 sqm toilets but do you only want the "bare essentials"? At 1.20 it was already really hard to find a sink where you can wash your hands properly without splashing everything wet. And the toilet alone has a depth of 56 cm. I don't want to impose anything on anyone but describing 2 sqm as spacious... I just couldn't let that stand, sorry

During the week we are in the living room mainly in the afternoons and evenings, hence the orientation to the south or west (in this case west), although we also see that this area is currently too small in the plan.

The question is, do you then use the living room only for watching TV or what do you do in it? For watching TV, the south/west orientation is not ideal since the shutters are closed anyway.

Living room mainly for watching TV, when guests are present, then usually at the dining table. I think the TV is best placed on the west wall to avoid such reflections. In general, we watch little to no TV during the day.

...
Give the sauna the best location and the living room in row 2? And completely disadvantage the bedroom right away. How often do you lie in the bedroom, how many hours per day, how often are you in the sauna, how many hours per day?
How often does one sit in the living room, how often in the sauna?

I understand that you want to create a nice wellness area, but always keep in mind how often you realistically use it. And definitely include that in the planning.

I would really start over, or consult a good architect.

following advantages: as you said, the sauna is rarely used in summer, but all the more often in winter, especially on weekends, also during the day. I think the wellness area in the south is ideal for enjoying the sun as well. During the week in winter it will not matter anyway, as it gets dark early then.

Is it really the case that the sauna is used more than the living room or kitchen in winter?
But okay, if you insist on your labyrinth, you can move the bathroom’s outside door closer to the sauna. That would have the advantage that you can put the garden cushions on the direct path through the bathroom into the sauna—for overwintering or in case of rain. Because I don’t think the sauna will be used much anymore once there are children.

But I’m out of here if the design is still justified, even though the sofa wall is less than 3 meters, the sink is no deeper than 20 cm, and one has to wonder how it can even be ideally divided.
The path from the washbasin to the toilet runs diagonally through the house, and you don’t understand the TV because in the utility room the washing machine is washing against the property in the kitchen. And that with 180 sqm. Ouch.
The existing problems and the questions raised were not addressed at all.