Floor plan house with granny flat - improvement suggestions?

since the wall thicknesses are generally 20cm inside and 40cm outside for me. He would be more precise there.

As a general rule, that is absolutely practical, and precision has no place in a preliminary draft yet! ...

except for the apartment partition wall, which is 30cm thick.

... just as much as this "bulletproof vest" in a house of building class 1. But I had already pointed out that this exaggerated large-caliber fire wall here is not only unnecessary but also a burden on the statics. Moreover, it also makes unnecessary thermal decouplings necessary, if you take it precisely. There generally belongs neither a concrete wall here nor in this generous thickness. I suspect that Zchenknecht is reminded of such a monstrosity from some multi-story residential project. By the way: I fear we have lost :-(

Could you please provide the dimensions of the individual rooms?

Here are a few reference points for the upstairs:

except for the apartment partition wall, which is 30cm thick.

Which is, however, completely exaggerated!

As a flat rate, that is absolutely practical, and precision has no place in a preliminary draft at all! ...

You should remember this sentence for all other preliminary and amateur plans. Because you criticize the brick size in almost every amateur plan ;)

You should remember this sentence for all other preliminary and layperson plans. Because it is precisely the stone dimension that you criticize in almost every layperson plan

No, and I sincerely ask for forgiveness if I have been understood by laypeople as criticizing them for it. Laypeople (and in preliminary drafts) I point this out – I criticize "architects" for it (and in supposedly submission-ready plans)!

In a preliminary draft stage
it is about planning a room layout – in such a way that it "works" even when no furnishings are wedged in with centimeter accuracy. For this reason, it is even "pedagogically valuable" if the layperson who is (co-)planning thinks/counts/calculates only in whole double decimeters secondly, and first of all does not even dream of confusing half-centimeter precise dimension specifications with the working precision in shell construction (see also "Where do the half centimeters come from?" at a well-known place).

In building application plans, on the other hand,
the plans should be judged by their ability to truthfully represent the conditions of the literally “construction drawings.” Stones can be cut more or less arbitrarily depending on the material (however, one does not need to deliberately create this necessity!) – but a consistently related bonding dimension must not be!
Therefore, it is proper for the diligent planner to not ignore the material working rhythm of the masons.

For those willing to build, this means: that they are well advised to think in 20 cm steps as long as discussions are still ongoing and when they create their own sketches; and to keep the octameter grid only "in the back of their minds" in order to "catch" their planner in case of possible negligence. This, mind you, not to please me or Gotthilf Penibel. But simply because ignored stone dimensions are the seedbed of botched jobs and violated bonding dimensions.
When in doubt, the layperson plans every interior wall as load-bearing based on spatial requirements and is then pleased when the structural necessity is satisfied with less in some places.

... just as little as this "bulletproof vest" in a small building of building class 1. However, I had already pointed out that this exaggeratedly large-caliber fire wall here is not only unnecessary, but also a burden on the statics. Moreover, it also requires unnecessary thermal decouplings if you look at it closely. There is generally no place for a concrete wall there, nor in this generous thickness. I suspect that Zchenknecht is reminded of such a monstrosity from some multi-story residential construction project. By the way: I fear we have lost :-(

What thickness do you think the WTW should have? We were told that a 30cm wall would be recommended due to sound insulation.

Of course, it also depends on the material, but especially as a partition wall it should be at least 25cm thick, since normal apartment walls are too thin. Which is completely normal with 11 or 12 cm.