Hello Artur Wawrzynkiewicz,
Thank you so much for your question regarding theme translation. You know about
mo file? If you can create a
.mo file, please make the .mo file of your own language and add that file on language folder on child theme. After switching the language from backend, it will automatically change it.
If you can’t you can change the text of that file by overriding from the child theme. Go as you want.