Location of guest WC - entrance area?

Yes, apart from the possibly unnecessary windbreak, it is a classic solution. But then again, dozens of "experts" write that the toilet window should not be next to the front door. Someone might hear when you flush the toilet before opening the door. I always wonder how often that actually happens in normal life.

Yes, apart from the possibly unnecessary vestibule, it’s a classic solution. But then again, tons of "experts" write that the bathroom window shouldn’t be next to the front door. Someone might hear it when you flush the toilet before opening the door. I always wonder how often that actually happens in normal life.

True ... then good sound insulation is necessary ...

I also find the location near the entrance door quite practical because you might need to use the toilet when you are working outside or just coming back from a walk with the dog and it’s a bit urgent. One observation I make is that our visitors "from further away" (>40km) ask for the toilet first. So it does make sense to make it a bit more accessible from the entrance area.

A toilet window next to the entrance door also makes sense. If the delivery person disturbs your session, they can just hand everything through the window.

We also think that the guest toilet, being easily accessible from the living area, has its advantages -> apart from the morning and evening routine, it is actually used much more by the family rather than just by guests. The same applies to the staircase. A floor plan always consists of compromises and is a matter of taste. Some things "result" from other wishes... I don't find your floor plan bad either, except for minor details. If you would like to present the upper floor as well or have further questions, you could also start your own thread.

The guest toilet in the entrance area is simply common practice here in Germany. In other countries, people make less of a fuss about it. A Spanish builder omitted the guest toilet in our row house development in 2001 in favor of a larger hallway. In many English houses, there is a WC squeezed in somewhere on the ground floor, but all bedrooms have ensuite bathrooms. What really matters is what you want yourself. Then you can safely forget some conventional things and prefer your own solution.

Are there good reasons for this ... why the guest bathroom

Of course there are counterarguments. But on the other hand, the living room, kitchen, and other rooms actually get more priority in the planning, so the perfect design of the bathroom simply has to take a backseat. And then there is also the argument of short pipe runs and the fact that you want to use the toilet first when coming from outside or also during gardening with muddy boots and dirty clothes, or filthy children—in that case, having it located by the front door is exactly what you want.