I have a Motorola Moto G with English set as the default language, but I also selected Polish as an alternative input option. However, when I change the keyboard input to Polish, English dictionary is still used for input correction and hints. How can I fix this?
You can fix the input text prediction by following: Adding a new spell-checker to Motorola Moto G
You can't add Polish to the list of Spellcheckers, but too be honest I am not sure where these are used. Google keyboard (which needs to be installed to use the text prediction in this language) lets you download a lot of dictionaries.