*spoilers*

I think Im stuck because of a quest bug. Im with the dawnguard and Ive just spoken with the Moth Priest in Fort Dawnguard. He tells me about th bow and stuff. Next I get a questmark, I need to speak to Serana. She told me about her mother and where she might be hidden, so I want to search for her. The strange thing is that the questmark doesnt change after this conversation with Serana. The game still asks me to speak to Serena, but she doesn't have anything important left to say that makes my goal change. I'm not sure what to do next, I have a feeling my quest is broken. What can I do?

Ok, I finally found a way to fix it in-game, but it's still something that should get fixed.

Sollution for those who have the same bug:
- Tell Serana: "I think we should part away."
- Ask her to follow you again.
- The missing dialoge will be available again.