Want to help in translation?
here is the file that is currently being used:
https://raw.githubusercontent.com/libretro/RetroArch/master/intl/msg_hash_pl.c
but seems like polish is missing one entire file that you need to translate from english
(only the strings between " " )
https://raw.githubusercontent.com/libretro/RetroArch/blob/master/intl/msg_hash_us.h
you can use Git to fork https://github.com/libretro/RetroArch and do a pull request: Help
or if you want you can edit them and pass them to me i will do the pr