will {m = 0, b = 0} not work?

scoringDefaultM{haut=1,p=0}

Begin{questionmult}{optionale answer}
Are there optional answeres?
Begin{choices}
\wrongchoice{wrong1}
\correctchoice{correct1}
\correctchoice{correct2}
\wrongchoice{wrong2}
\?wrongchoice?{optional} <- If you check this it don't matter for scoring. Possible?
end{choices}
end{questionmult}

I don't get it...

\scoringDefaultM{haut=1,p=0}

Begin{questionmult}{optionale answer} /scoring{haut=1,p=1}
Are there optional answeres?
Begin{choices}
\wrongchoice{wrong1}\scoring{m = -10, b = 0}
\correctchoice{correct1}\scoring{m = -10, b = 1}
\correctchoice{correct2}\scoring{m = -10, b = 1}
\wrongchoice{wrong2}\scoring{m = -10, b = 0}
\?wrongchoice?{optional}\scoring{m = 0, b = 0}
end{choices}
end{questionmult}

I tried something like this and a couple of other things but i guess i just did not understand the scoring it self :-(

this

\wrongchoice?{optional}\scoring{0}

This is not working.
_\scoringDefaultM{haut=1,p=0}

Begin{questionmult}{optionale answer}
Are there optional answeres?
Begin{choices}
\wrongchoice{wrong1}
\correctchoice{correct1}
\correctchoice{correct2}
\wrongchoice{wrong2}
\wrongchoice{optional}\scoring{0}
end{choices}
end{questionmult}_

If all correct answeres are given and "optional" is marked the result is still 0/1.

I had never used haut
My suggestion : use formula and a test.

\scoringDefaultM{default.optional=0,formula=(NBC==NB && NMC==1 && optional==1? 1:0),p=0}

\begin{questionmult}{optionale answer}
Are there optional answeres?
\begin{choices}
\wrongchoice{wrong1}
\correctchoice{correct1}
\correctchoice{correct2}
\wrongchoice{wrong2}
\wrongchoice{optional}\scoring{set.optional=1}
\end{choices}
\end{questionmult}

This works fine for me:

\element{qqs}{
\begin{questionmult}{added}
What is the correct answer:
\begin{choices}
\correctchoice{correct1}
\wrongchoice{optional}\scoring{b=0,m=0}
\wrongchoice{wrong1}
\correctchoice{correct2}
\wrongchoice{wrong2}
\end{choices}
\end{questionmult}
}

Whether the optional answer is checked does not change the score of the item. The item is worth 4 points total rather than 5 points (i.e., the optional answer is ignored). Is this not what you are looking for?

I think you do not use the same global scoring strategy

\scoringDefaultM{haut=1,p=0}

and for you

The default scaling for a multiple question is e=0,v=0,b=1,m=0,p=-100,d=0

The default strategy haut=1 overwrites the d and p values with d=1-N (add 1-N to the total, where N is the number of answers) and p=0 (floor).
If you set b=0 for the optional question, so that checking it or not will lead to the same result, you need d=1-N+1 instead (and again p=0). And you also need to cancel the haut=1 for the question, so that d won't be overwritten:

\begin{questionmult}{optionale answer}\scoring{haut=,d=1-N+1,p=0}
Are there optional answeres?
\begin{choices}
\wrongchoice{wrong1}
\correctchoice{correct1}
\correctchoice{correct2}
\wrongchoice{wrong2}
\wrongchoice{optional}\scoring{b=0}
\end{choices}
\end{questionmult}

I didn't had Time to check if this works. Sorry.

In this case the result is always 0. not matter if i mark correct, correct and optional or wrong answeres.

This looks good. as far as I tested...

\begin{questionmult}{testfrage}\scoring{mz=1}

\begin{choices}[o]
            \correctchoice{richtig}
            \correctchoice{richtig2}
            \wrongchoice{falsch}
            \wrongchoice{falsch2}
            \correctchoice{optional0}\scoring{b=1,m=1}
            \correctchoice{optional2}\scoring{b=1,m=1}
        \end{choices}
    \end{questionmult}