Restricted construction site visits and cancellation of all appointments due to Corona

react by getting the contact details of the construction manager and he gets yours, and check everything at the construction site after 5 PM, and call and email your wishes and defects, so that the company does not do whatever it wants and always the cheapest

Exactly those are my concerns. However, permanent site visits after 5 PM cannot be a solution, especially during the autumn/winter period.

I would like to read that sentence once, formulated clearly.
I see no connection between contact violation and extension of construction time. Then one would actually have to assume that you have C and therefore it is already known in advance that the craftsmen will get infected and that is why there is a construction delay.
I therefore consider a "threat" to be very inappropriate.

The polite tone would say: despite the low numbers, please keep your distance, wear a mask, and conduct necessary conversations outdoors. In my eyes, that would be proportionate.

(...) "Only in this way will it be possible for us to complete your Viebrockhaus on time." ==> Original quote

(...) "Only in this way will it be possible for us to complete your Viebrockhaus on schedule." ==> Original quote

Given the reality on construction sites, I would not have read that as a threat, but as a conclusion that quarantine or illness simply do not do the construction progress any good.

Another company using Corona as an excuse to make life easier for themselves. If you know the conditions under which the sub(subs) work and are housed, it’s a bad joke. I would just ignore it and go to the construction site whenever it suits you.

Another company using Corona as an excuse to make life easier for themselves.
Knowing the conditions under which the sub(subs) work and are housed, it’s a bad joke.
I would just ignore it and go to the construction site whenever it suits me.

He can do that, no one is forbidding him. The contractor did inform the OP, even in writing.

I understand that this procedure is a restriction for you. I do not see a threat in the letter. Your contractor has apparently established a hygiene concept and rules of conduct. This suggests that the Covid-19 situation is also part of the construction schedule and craftsman coordination. That is definitely positive. The letter is probably sent to all property owners as long as the pandemic officially continues. I would not be concerned in the slightest. Call, ask, talk to the site manager, and find a way to live with it together. Distrust is a poor adviser, as is good faith - so clarify the questions directly instead of making assumptions.