eddy1234: If your char really freeze when approaching elfrith, I guess the only way you can do is to load back an earlier save, and retry it again. From my experience, elfrith can be save without even approaching hermosa, but I not sure hermosa's death will bug the quest or not. All you need is a book which elfrith gave you after saving him, and take the book to place at the northern part of the map, where there a grave and 3 candles. The location of that place is marked on your map, since its from the main quest trail. When you arrive there, just use the book to stop the wind in the area and lid up all the candles to proceed with the quest.
Laiv: if you are referring to the trader which encounter on the road in fjords, you need to use the trade button instead of open the trade menu through conversation. Its a known bug for a very long time.