How to get updated language packs?

In my language Ubuntu 12.04 translation is not complete. Now I want to complete the rest and want to add fully completed translation with the existing Ubuntu 12.04.

Is it possible? How can I do that?

I've just found that, we get the language updates through regular updates. But I need to know, how much time does usually needs to get the new updates of a language? I mean, suppose, I've submitted a new translation, then how much does it take normally to see that translation on running Ubuntu?

I'm really new about these translations matters. So, experts, please help.

1.) what is your native launguage? If you're wondering about an incomplete language pack, you can install the rest by gong to settings, languages then select to install the rest of the language packs by sleeping "check for new language packs" or something like that. I am assuming your native language is English and the message you are talking about is pertaining to incomplete languages being installed because you didn't select the "install third party apps" during install. If your language is not natively English then I bet the add on language packs that are available through settings will supply you with the languages you want. If you want to submit a translation then you can do so through the "translations" sub form on this board.

@Zestypanda, Thanks for your reply.

My native language is Bengali and only 25% is completed for Ubuntu 12.04 (precise). For this reason, I want to do the rest with some dedicated people and want to see the those translations running on Ubuntu 12.04. That's why I asked this question.