So I went to the bottom of the citadel dungeon and found christoffer de malamert. He explained to me that the seneschal is a traitor and gave me a quest. But then he kept attacking me. Is that normal? And I can't kill him either.

solved. reload 3+ and he greened.

No, it's not normal. He should stay neutral.

Does he always do that? Because he starts off hostile, so your character might have attacked him.

Reload and try again OR after the conversation (if he stays green but attacks) run for the portal, go through it and come back.

try to speak with him again... it works to me.

Thx y'all. solved.