I heard that there is an option to retake second profession after ascension?

well, that's what people said IG. some person in the Arid Sea you talk to? havn't been able to find anything about it on the website here though, great that it is.
did a search in forums too but didn't find it.

also, some of the Builds on this site for rangers contains 2 elite skills. either both ranger or 1 ranger and 1 secondary elite.

There's quests for every profession you can change to in seeker's passage, destinys gorge and heroes audience.

thanks. cant believe i missed those. ^^

You have to go to Daknars and see Vanti to get the ball rolling and he will tell you who to see where

but u have to ascend first

Which is why the OP said in his title "after ascension".

About the 2 elites build: those builds are from before those skills were turned into Elites. Prime example: Hundred Blades builds.