So here is the situation right now.

As i said been playing with a lot of different settings, or better said the way postfix an spamassassin are configured.
But all without the improvement i hoped for.

So i thought let's start over again, brought everything back in the the state is was before and how it's after a clean install from CO.

Funny thing is that these particular spam mails stopped coming in, i don't see them in my logs anymore. And the regular spam is still stopped.