Thanks. According to your suggestions I downloaded QTLinguist,our tranlations from Lauchpad and tried to release it to see in Mixxx. Unfotunately something goes wrong and output ".qm" file id much bigger than rest of translations (about 100kb) and Mixxx doesn't load it (although translation exists on available languages list). What am I doing wrong?

One more question: I aproved some old suggested translations, made almost 200 new and still working. How can I inform the rest of previous polish translators about it? I wold like to be checked and push my work forward.
Edit: I just checked recent activity of all polish translation members and unfortunately only one of them did something on Launchpad in last 2 months

I wrote him an email asking for help. Now I wait for aswer. Considering this fact, the best thing I can do for Mixxx and our translation is keep working writing suggestions and waiting for help. If there will be nobody able to help and accept my translations, I'll do it myself.