i have killed the Fampyr king without talking to him, now the quest doesnt update, does it matter for later on?

 

please maybe someone knows or i have to reload

You should be fine to proceed. The conversation with that character, while interesting, is entirely optional.

It is nice to talk to him to get more information about his people's fate and about his views on their work. But anyway it is optional and you dont get anything if you do not kill him, in fact killing him =experience. So, it is up to you. I did not kill him as I was lazy that day.

But anyway it is optional and you dont get anything if you do not kill him, in fact killing him =experience.

Doing the quest for him also = experience, I don't think it matters much (remember that you don't actually get experience for killing per se in Pillars)

I would rather talk to him and leave him be just for the RPG reason.