I played Dawnguard a while ago already as a Member of the Dawnguard.
Now I want to play it as a vampire, but the first time I can go to the castle (Quest: Bloodline)
Serana doesn′t talk to me and I can′t get in the Castle, just nothing happens.

open console and enter these codes:
player.moveto 020033b3
prid 02002B74
moveto player


These codes worked for me when I have the same problem, and I was able to enter and exit the castle afterward.

Thanks I am know in the castle but the gate at the front is closed like before D:

You mean the front gate that is supposed to be opened by an old guy? Or the front door?

the front gate is closed