Planning outdoor area - positioning the terrace

The garden seems too sterile to me and the large amount of sealed surface

yes, I think it's very nice. The pool is located, to be exact, in the southeast. The corner window cannot be opened. I understand what you mean But it's all a matter of taste. Overall, I find such a - let's call it - terrace island, which is also connected to the house, very nice. Moreover, you can still make it very cozy and not so open all around with grasses, nice lighting, stones, etc. On the south side, there is the neighbor's driveway, whose house would be directly in view. If I place a 4m wide terrace on the south side and also plant hedges that block my view of the neighbor's block, I am looking at a green wall

To me, the garden seems too sterile and there is too much sealed surface

I completely agree with you. However, I really like the idea of placing the terrace at the corner and the pool on the south side.

Better a green wall than a drafty corner.

But everyone has to decide that for themselves. I only see that many well-intentioned terraces are not used because they are so far away from the kitchen (and then you rather prefer the small seating area at the kitchen terrace door) or because they are simply not protected by anything and every breeze is noticeable. We humans are prey animals and prefer the feeling that we are protected in one direction and don’t have to be on guard there.

Although the evenings when you can sit freely in the garden and welcome every breeze happily will surely increase due to climate change, overall there are probably more evenings when you wish for a warming wall and a wind-protected spot.

The pool is planned to be 8x4m. I'll say it boldly: too small to actually swim in, too big for a "paddling pool" that you like to jump into in summer to cool off. And all that effort with circulation pump, cleaning, etc? Really?

I would seriously consider a natural swimming pond. It is much less maintenance-intensive, no chlorine needed, you can jump in (just like in a lake), natural and eco-friendly. And also nicer to look at than a blue rectangle in the garden, which looks even uglier in winter. Take a look at that! It also visually enhances the garden overall.

I would create a cozy chill-out area on the south side, where the drafty presentation plate terrace is currently planned, I would make a natural pond there, which you could connect directly to the wooden terrace (there are many examples on the internet – very beautiful! If I had space for it, I would do it immediately), with only a relatively narrow passage to the other terrace, which is directly next to the kitchen there. I would make that nice and cozy, possibly even with a small wall (where you could integrate a grill or garden fireplace). After refreshing in the swimming pond, you can lie down directly on the wooden planks of the south terrace (I would definitely make this terrace out of wood) and let the sun shine on you.

While a pool is a pretty ugly affair if it's not perfectly maintained and is just a hole in the garden in winter, a natural pond is always a pretty sight. The shore zones are usually laid out with pebbles and some plants (which clean the water) and you can see the change of the seasons there. Such a pond can also have natural shapes (because you wanted something more playful in the garden), but it can also be designed geometrically.

Because something like 8x4m – honestly, that's neither here nor there.

The pool is planned to be 8x4m. I'll say it boldly: too small to really swim in

Objection
I find this size very pleasant...

And also nicer to look at than a blue rectangle in the garden, which is even uglier in winter

But that is very subjective...

Your preference for ponds is respectable, but let people have their taste and wishes, for example, I never wanted to bathe where I can't see the bottom and little creatures are swimming around, everyone is different, but I think you’re pushing your opinion too much here, no offense