Floor plan optimization - semi-detached house approximately 150 sqm

You have received tips on how to determine whether the floor plan suits you or whether the intended is possible. You will not find another floor plan of a semi-detached house of this size with 2 apartments. I am not clear about what you want.

An example floor plan that I can learn from or 2-3 tips would help me.

The reason no example floor plan has come so far is probably because there is no one here who has built such a semi-detached house with the specifications. You may not want to hear this, but the idea of having the possibility of two separate apartments in this semi-detached house is simply not the best for many.
In addition, there is the issue with the stairs because of the basement, which others should please imagine for themselves. It is also unclear what kind of roof shape, whether there are sloping ceilings on the upper floor or not, etc.

A 1960s farmhouse is actually okay, by the way. It just shouldn't be too tight or stupid.

But that it is too tight in some places has already been written several times.

Personally, I would never come up with the idea of spending so much money on a new build just to have small rooms and live cramped, only to keep open the possibility of 2 residential units for sometime in the future.

This "discussion" reminds me of my music teacher back then… His saying was often: "There are three groups/categories of people. Those who get it immediately, those who need a bit longer, and then there is a third group." :D (will probably be deleted immediately because, after all, it brings no added value :))

The reason no example floor plan has been provided so far is probably that there is no one here who has built such a semi-detached house with these specifications. You may not want to hear it, but the idea of the possibility of two separate apartments in this semi-detached house is simply not the best for many. In addition, there is the issue with the stairs because of the basement, which others should just imagine. It is also unclear what roof shape, whether there are sloping ceilings on the upper floor or not, etc.

Ok, then leave out the two-apartment concept. What would be the difference? Bathroom smaller downstairs, guest room somewhat. But otherwise? Stairs have to be there because of the basement.

Below: Storage room stupidly placed / integrated. When you enter, you walk into a wall, wardrobe not properly integrable, bathroom too large, poorly furnished. Dining area poorly planned, same with living area.

Above: Poor room placement Children’s room facing north = cooler, but less sun Gloomy, too large hallway Bathroom unnecessarily prominent in a good room position Children’s room with unfavorable door placement

Just as an introduction. Detailed information and descriptions will be provided if you no longer hesitate to supply all necessary information.

You received tips on how to determine whether the floor plan suits you or whether the intended plan is possible. You will not find another floor plan of a semi-detached house of this size with 2 apartments.
I am not clear about what you want

Downstairs:
Storage room stupidly placed / integrated.
When you come in, you walk into a wall, wardrobe not properly integrable, bathroom too big, poorly furnished. Dining area poorly planned, same with the living area.

Upstairs:
Room placement poor
Children's room facing north = cooler, but less sun
Gloomy, too large corridor
Bathroom unnecessarily prominently placed in a good room position
Children's room with unfavorable door placement

Just as an introduction.
Detailed information and descriptions will be provided if you are no longer too proud to provide all necessary information..