You can use MB3Editor to create mod firmware
1. Create modded firmware -
Index - MB3Editor
Select default language for editing >
Polish
✔️Translate Firmware? >
English
✔️ Set default language?
✔️ Change number of notifications?
✔️ Use notifications fix? For languages with another string for 5 and more notifications.
2. Edit Resource -
Index - MB3Editor
Select default language in firmware >
Polish
✔️Add translate days? Select language for days >
Days EN