Independent building expert or protection association?

Hello again,

I still have to ask a question here. We have now decided to safely bring in a building expert for our new construction. However, we dealt with the topic a bit late, so the contracts etc. have already been signed. But construction has not yet started.
Where I am currently stuck is the fact of where the added value would be for me, for example, in the [Bauherren-Schutzbund]. It costs an initial fee as well as a monthly contribution. Can't I just take an independent expert? In the [Bauherren-Schutzbund] he is supposed to be a bit cheaper. Does it bring any other advantages?
For the legal support, I have legal expenses insurance, or am I misunderstanding that?
I would be grateful for any tip or two.
Oh yes, the construction is in the south of Bochum, in case someone can give a recommendation.
Thanks to you all

It does not even have to be an expert. There are many engineering firms that employ experienced civil engineers. I have had good experiences with hourly billing.

Legal protection does not apply in 99.9% of all cases for new construction, you have to check the conditions ...

And please do not just look for an expert over the internet, we totally fell for that ...
he should possibly be a sworn expert, then you are on the safe side ...