Hey Lukasz,
You’d probably have to change it via whichever translation app you’re using.
If you did the translations manually (yourself, rather than via an app), then you’d need to follow the steps listed here (https://help.shopify.com/en/manual/markets/languages/translate#exporting-importing-translations) for doing an export of your translations to CSV > editing them > then importing them back into your store.
I always recommend using the T-Lab app (https://apps.shopify.com/content-translation) for handling translations, as it’ll auto-translate for you, and also make it easy to manually edit translations quickly (without having to do any importing/exporting).
Hope the above helps point you in the right direction! 
Cheers,
Stephen