pardon me and my silly question but ._.
is it worth to get pokemon b2/w2 even if i have both black and white already? :/
It's all up to you whether you want to get the games.
I'll just add on to what Zupplu said. Black 2 and White 2 take place 2 years after the story of Black and White.
There are new locations, and the Pokedex is now a mix of Unova Pokemon and Pokemon from previous generations. There are also new Gym Leaders and new features.