Weekend house up to 150 k€ in BB

Have an offer for an 88 m² bungalow [...] What do the experts say about it?

I prefer the title specialist, "experts" are the windbags on talk show panels ;-)
I would take the basic model as is and change two things: on the one hand, extend the house axis in the grid by about a second children's room (that would be my family stuff room not rented out), on the other side of the hallway, the extension would benefit the living-cooking area and also create more space for a fireplace there; secondly, I would create an open roof soffit (careful: acoustic ceiling!) with roof windows above the living-cooking area. In the utility room there is (without modification) still space for a broom closet with a built-in safe.

that is interesting, the tens of thousands of weekend properties of Berliners in the surrounding area are becoming fewer and fewer, as they are now too expensive for a hobby/relaxation. You want to buy/build exactly that expensive. The logic for me would be, then really age-appropriate, barrier-free (is a luxury in younger years), modern heating. Use it now as a weekend house and rent it out, with the option to move in later, sell or whatever. don’t throw money away for an interim solution.

that is interesting,
the tens of thousands of weekend properties of Berliners in the surrounding area are becoming fewer and fewer,
because now too expensive for a hobby/recreation.
You want to buy/build exactly that at a high price.
The logic for me would be,
then really age-appropriate, barrier-free (a luxury when young), modern heating.
Use as a weekend house now and rent out,
with the option to move in later, sell or whatever.
don’t throw money away on a temporary solution.

How are your opening words to be understood? Is that criticism of the project or encouragement? We have also discussed the topic of age-appropriateness => senior residence. I just wouldn’t know what one should do in old age in the village. Especially then you need short ways to shopping, doctors, culture. None of that is there. Therefore the fear of planning now for a scenario in 40 years that will never happen and in the meantime has cost extra money. Heating can then or probably must then be replaced anyway, because worn out. Or am I overlooking something?

I prefer the title specialist, "experts" are the hot air balloons in talk show panels ;-)
I would take the basic model like this and change two things: on the one hand extend the house axis in the grid by about a second children’s room (that would be my family stuff room not rented out), on the other side of the corridor the insertion would benefit the living-cooking area and also relieve the space for a fireplace there; secondly I would realize an open roof underside (caution: acoustic ceiling!) with roof windows above the living-cooking area. In the utility room there is (without changes) still room for a broom closet with built-in safe.

Interesting idea! Of course, every further enlargement costs quite a bit of money again. Family stuff could also be stored in the cold attic of the bungalow. Whether that is practical is another question. I would like the open roof underside. I have to ask how the roof will be insulated. I believe only the ceiling of the top floor is insulated in the standard?

Last week we looked at the hybrid house (occupied show house)

We liked it very much too. Although I still had doubts about the summer heat protection regarding the glazed dome.

And what are the opinions on the Schwörerhaus Flying Space? At first it seemed utopically expensive to us, but after deducting the subsidy and considering the low costs for the foundation, not so uninteresting anymore.

How are your opening words to be understood? Is that criticism of the project or encouragement?

Encouragement The old weekend houses had no heating, i.e. were not winterproof and are being abolished one after another. Single-family houses and multi-family houses are being built and inhabited on the plots. Therefore, build properly, your light plan already costs 200-300K€ and that as an interim solution?

I just wouldn't know what to do in old age in the village. Especially then I need short distances to shopping, doctors, culture. None of that exists there. Therefore the fear to now pre-plan for a scenario in 40 years that will never occur and in the meantime has cost additional money.

What will be in 40 years, neither of us knows, maybe marauding gangs will roam through Berlin, or a self-driving car will take you to the doctor and shopping, or or or. I would build a proper house and not just a summer residence

Family stuff could also be stored on the cold floor of the bungalow. Whether that is practical is another question.

The question implies their answer is no.
I wouldn’t want to fetch my non-tenant bed linen and my non-tenant coffee cup etc. from the pull-down attic stair storage every time I use it myself.

And what are the opinions on the Schwörerhaus Flying Space?

Outside there are only little pots: in my perception, the organic label surcharge applies in the entire market segment Tinyhouse & Co. Minimalists value their world-saving mission at an avant-garde price level, and in market economies a basic principle is that purchasing power wants to be tapped.

I also find the first floor plan suitable for the purpose. I might consider removing the current "Gäste-WC". Slightly reducing the room size would give more space to the wardrobe, and the remaining area could be integrated into the bathroom as a walk-in shower. Personally, that would be more important to me in my vacation home than a separate WC. But just as a suggestion, after all, you must have had a reason for it.