How fast can I ask Serana about "cure" lycanthropy? May I to do it during first transformation or Silver Hand Quest? I don't like werewolves, but... but... Ok, good. I'll make a new line for game saves and play as a true Companion.

P.S. Dawnguard DLC ended by a vampires side.

Serana doesn't cure your lycanthropy,you must continue on with the companions quest to do that.

Asking Serana to become a vampire lord cancels out your Lycanthropy, so if you're not currently a vampire lord you could speak to her. I believe that's how it works, at least.

I'm a vampire lord now, but Silver Hand quest start already. Aela and Skjor is waiting for me in the Underforge.

Wait,how did you become a vampire lord and a werewolf at the same time?

I thought that was impossible.

I'm a vampire lord already (and been it long time before) And Aela and Skjor is waiting in the Underforge for me. I must to drink Aela blood, but I don't want to be werewolf. I want to revert back to vampire lord after that quest as fast as is possibly.

Oh I see

I'm not sure but I think Serana will turn you back into a vampire lord any time you want,save your game first just in case.

I know you will have the option to get her to turn you into a vampire lord right before going into the soul cairn.

If you have already done the soul cairn quest and Serana doesn't change you back then you will have to wait until the end of the dawnguard quest line.