Hi Zoran,
I was looking through the TWN statistics overview page for all social tools and it seems that for Serbian (Cyrillic script) only 26% of all the messages are translated, and for Latin script the situation is fascinatingly even worse with only 18% translated. I'm wondering if you'd have the time and the interest in improving the Serbian i18n for social tools? :-) (Note that according to the statistics page, only Turkish (tr) translation is 100% complete, but as I maintain the Finnish (fi) translation, which is "only" 92% complete, I can safely say that 92% is more than enough for a usable user experience; the remaining 8% is stuff like Special:Version descriptions and API i18n, which are not very likely to be seen by users in most cases.) If you do decide to tackle this massive project and need any help, don't hesitate to contact me! While there obviously is message documentation these days, it's probably not anywhere near perfect and oftentimes a screenshot or two can be a lot more helpful.
Mnogo hvala!