(i got the DLC) i've tried almost every guard in Whiterun like the Wiki says , and i cant find the quest , do i need to join the Imperial Rebelion before? cuz i cant found it and i'd like to have Serana as a follower.

Thx

the guards will start mentioning the dawnguard after you hit level 10, if you are planning to start it before then you have to find the castle yourself.

im 22 , and i tried to find it , it says i cannot go that way , and there is no cave

I'm 95% sure you have the LE and don't even have Dawnguard installed.

Answer me this:

Do you have vampire attacks?

Can you craft arrows?

fk , u're right , i was looking for the fkin arrows today and i didnt saw them, wut , i installed dawnguard with my friend like months ago o.o

Your next step would be to install DG.

ye i know , i have it on my computer , will i lose saves?

Nope. Once you install the DLC your character will not lose any progress. Just be careful if you fast travel to cities....