Construction diary of the new build of a city villa with garage

Where did you get that from?

You can even pour concrete in freezing conditions. It depends on so many circumstances, so making such a general statement is questionable.

Many things are possible! Nevertheless, in many places it is initially recommended not to pour concrete below 5°C or in freezing conditions. It looks different if the concrete is "prepared" for this purpose by, for example, additives or adjustments to the mix/choice of concrete, etc. But in freezing conditions, you cannot just pour concrete like that, and if a foundation is poured up to 90% and the rest follows at some point, then I would definitely clarify whether the concrete (if there are correspondingly low temperatures there) is suitable for that.

If you have enough time, you can't go wrong with your rule. It doesn't cost anything initially. Only if there are construction delays will it probably become much more expensive than the modified concrete mix, concrete temperature, and altered curing.

By 90% I mean the foundation. See pictures. Whether this is a problem is currently being examined by an independent [person].

The base slab was poured at around 0°C. It had special additives and looks neat according to the expert. Strip foundations were still at >+5°C.

Don't you have an architect or construction manager who keeps an eye on the mess? You don't seem to have much to do with building. How did you award the construction contract?

The foundation, as it was made, has no static function anyway, but serves only as frost protection. The joint then also does not play a role. Nevertheless, you should find a knowledgeable construction supervisor.