House construction is starting. How exactly to register helpers?

Hello

We are now starting with the house construction. We want to complete the shell construction by ourselves, as well as many other small tasks. Friends and family who are very knowledgeable will come to help.

How exactly do I proceed? I read that I have to register all helpers with the Berufsgenossenschaft der Bauwirtschaft and pay €2 per helper hour.
Do I have to register all helpers by name in advance? Because during the construction phase, other people will probably join.
Or do I just have to notify when the construction starts, keep a construction diary with all names and hours, and submit it after the house is completed?

I have some acquaintances/friends who are not family, but want to help for FREE. How can I protect myself or prove that they are really not working illegally and are doing it as a favor?

Is there anything else I should consider?

It is also important that you inform yourself about how and what the insurances cover. Keyword warranty.

If your grandpa does the electrical connection for you because he maybe learned it once, but later it causes a short circuit and the house burns down.

I don't know if you can insure something like that, but I would think about it and inquire. Or who pays if a helper gets injured. As far as I know, there are insurances for that.

Just some tips.