He sees you when you're sleeping; he knows when you're awake ...
He knows if you've been bad or good.
Re: Trank der Schnelligkeit / Speed potion
Yes. The only requirements are that the APs can only be used on that turn by the character who drank the potion, and that the golden rule about completing an action before starting another does not get violated. Other characters may take actions, and then you can return to the character who drank for another action.
This is correct - as long as the same character who drinks the potion uses all four potion actions, they can be alternated with other actions as you wish.