Construction costs single-family house bungalow

Well, what does low standard mean? In Germany, the "low standard" is already completely sufficient.

Standard does not mean poor quality material, but rather, for example in electricity, usually only a minimal number of sockets. For instance, there was recently a thread where 34 sockets were listed for an entire house in the description. I find that already quite few.

The prices are ok. The costs for tiles and so on are open-ended. but for 25 per sqm gross there is something decent. GaLa Bau too low, you need 20 thousand with plants etc. pp. Kitchen missing. Carport? Garage? Garden house? However: on the whole it is realistic.

You gave yourself the answer. That won't be included at that price. Apparently, ventilation is already standard for you :). €7k for tiles including material is not much either. The OP treated themselves to something nice just with the windows. Since the offer is relatively high, €3000-4000 more. Either they are not plastic windows or made of wood.

Yes, ventilation (whatever kind) is now standard for me. I hardly know any houses without it among the providers.
The price per square meter for the tiles would be interesting. €7000 can already be generous if hardly any tiles are used.

Standard does not mean poor quality, but, for example, as with electrical installations, usually only a minimal number of sockets. For example, there was recently a thread where 34 sockets for a whole house were listed in the description. I find that already quite few.

Alright. I was referring less to the quantity and more to the quality. Regarding the quantity, everyone has to decide for themselves what is sufficient.

I had also already considered a ventilation system but unfortunately read that these are very expensive. Is there an inexpensive option? Carport will be built later on own initiative. What do you think about the masonry, it is not the best stone now, is it?

So I don't want to be without my ventilation system anymore. Alternatively, there are also window rebate ventilations. Since houses nowadays are so tightly sealed, you actually have to ventilate repeatedly. Especially KfW houses are almost hermetically sealed. We have KfW70. We would have to ventilate approximately every 2 hours to really prevent mold and mustiness. Our ventilation system once failed for 4 hours. We noticed that within 30 minutes. The air quickly became stagnant.

I had also already considered a ventilation system, but unfortunately read that these are quite costly.
Is there an affordable option?

The carport will be built later on my own initiative.

What do you think about the masonry? It's not the best stone, is it?

If you want a higher quality house, then you also have to pay more.
For the indoor climate as well as for the stones... and everything else ;)