I’d like to describe how simple way to configure polish characters/locale inside terminal.
cat /usr/share/i18n/SUPPORTED | grep "en\|pl" > /var/lib/locales/supported.d/local
This example shows all polish and english localization. You can find appropriate inside /usr/share/i18n/SUPPORTED file. If you choose add them to list.
dpkg-reconfigure locales
update-locale LANG=pl_PL.ISO-8859-2
In this step you choose langauge of your system and terminal.
locale