Every English-speaking developer has written this line at some point:
const label = count === 1 ? `${count} file` : `${count} files`
$label = $count === 1 ? "{$count} file" : "{$count} files";
It works in English. Now hand it to a Polish translator. Polish has three forms of "file" that matter here: 1 plik, 2 pliki, 5 plików. Your ternary only has room for two. Whichever two forms the translator picks, a Polish user will see broken grammar somewhere between 2 and 24 files.
The problem isn't the Polish translation. The problem is that the code decided how the sentence works before the translator ever saw it. This chapter is about giving that decision back to the people who know the language.