Minetest is always looking for translations:
https://dev.minetest.net/TranslationIn Minetest, both the game engine as well the games and mods for the games can be translated. When you want to translate a specific game. If you have questions about translating Minetest, you can always ask in IRC:
https://wiki.minetest.net/IRCThe Polish translation exists, but it always needs updating after a new release. Currently, it is at 75% for Minetest itself. For games for Minetest, the percentage is usually lower. If you're looking for a specific game for Minetest to translate, try Repixture, one of my own games.
https://content.minetest.net/packages/Wuzzy/repixture/If you're looking for a larger project to translate (meaning about 10000 strings), look no further than Naev:
https://naev.org/I am helping with translating this myself, to German. This game is still in development, but already has a large number of texts to translate and there is no Polish translation yet. As the Polish translation must still be created, contact the dev team here:
https://naev.org/contact/I recommend to start translating this one only after you've played this game for a while or at least are loosely familiar with the game, so you get the context right.
Both Minetest and Naev are translated on hosted.weblate.org. But games and mods for Minetest are translated with text files, which is more annoying (check out the wiki site) but at least they *can* be translated in the first place. :-/