New build bargain house from Poland, what to consider?

Hello community,

Through an acquaintance, I became aware of a Polish house construction company XY (existing since 1990).
The house including garage from the acquaintance is already standing and currently only the interior finishing is being done. The process for him was approximately as follows:
German architect, structural engineer, and site manager were commissioned
Desired house planned by the German architect and sent to company XY.
Received offer from company XY and signed after consultation with the architect.
Company for the basement was commissioned
Company XY receives 30% of the house price as a down payment to order the materials.

The acquaintance had some things changed in the offer, external insulation, changes to the free fireplace... final price €170,000 for 180m² on 3 floors + extras.

Now the interior finishing such as wallpaper, tiles, sanitary facilities... which he is doing himself, is added.
The company itself offers interior finishing only in connection with a partner company from Poland, but considerably cheaper than through a German company.

What is still to come now is the gas boiler, the solar system on the roof, and connecting the whole house (electricity, water, gas...)

Here are more details & my first received offer for a 150m² house on 2 floors, here nothing has yet been planned with a German architect. I want to build without a basement, only on slab.

Our standard version:

[*]Interior finishing – painted wood, drywall construction, wooden boards and tiles;
[*]Facade – wooden facade, acrylic plaster with full thermal insulation;
[*]Roof – roof tiles, metal, bitumen sheet.

Now my question to the professionals is, with what final amount one would have to reckon approximately in Baden-Württemberg, so everything completely including slab, connections, architect, structural engineer, site manager...

How do you hold the company liable for possible defects if the headquarters is in Poland?

The site manager should recognize serious defects before payment. According to the acquaintance who is already building, he has already spoken with several other homeowners of this company, and in case of defects, the boss usually came by quite quickly with 1-2 employees and tried to fix it immediately.

I agree with daniels87. It may certainly be true that a Polish company is obligated under German law to remedy defects. The question then is how to enforce this if the company does not comply. In that case, a Polish court may be responsible.

You are too naive if you believe a site manager has enough time to see all errors. We had a site manager from the general contractor (who supervised well over 20 construction projects) and in addition our own expert. Still, a mistake was not recognized in our case. After 2 years, the entire house had to be replastered. It took about three quarters of a year, some letters, emails, and phone calls. Overall, however, the mistake was acknowledged and has now been corrected. Fortunately, we did not need a lawyer or a court.

Payment is made according to the progress of construction?

Example: The construction has progressed. A defect is discovered but not acknowledged by the company. You make no payment, the company does not continue building. What then?

BTW: Is your acquaintance building two houses? One with a hip roof and one with a gable roof?

Well, I can already see the risk is quite high, but I would still be interested to know whether any savings would be possible at all or if in the end you pay the same as with Massa Haus, Danw... and Co.

P.S.: I just blindly took the pictures from the Facebook page, didn't pay attention that they used different houses as "we are building a house in Germany Endingen." The first house with the gable roof is the one, though, I have already been inside it.