I have already downloaded French translation(with .so extencion), not actually downloaded.
This does not make any sense.
The rest of your post does not make any sense either
I think you would like your applications to speak to you in French. That's OK: Linux is good with very many languages, but I am fortunate, and just use English.
Perhaps you will find better advice on a French
forum for linux? There must
be French forums for linux. Please find them and ask your questions there. When you find the solution, please post it back here, so other French users can find this thread, and your links and the answer.
Otherwise, when you installed your linux distribution, you were probably asked where you lived (and what Timezone you are in), and what language you prefer. If you answered these questions correctly, your distro should have been set up properly for the French language, keyboard and character set. If this is not the case, then perhaps you should re-install, selecting the correct language and location choices.
Mandriva is, I believe a "French" Distro. You might have better luck with that.