Learn Polish: Ten znany krawiec uszyje ci je bardzo szybko. - This famous tailor will sew them for you very quickly.

When you have multiple short pronouns next to each other, Polish has a strict ordering rule. The Dative pronoun (the indirect object, here ci meaning "for you") almost always comes before the Accusative pronoun (the direct object, here je meaning "them").

Could I put ci je at the very end of the sentence?

It is highly unnatural to put short pronouns like ci and je at the absolute end of a sentence if there are other words available. Short pronouns act like little phonetic attachments and prefer to hide inside the sentence. That is why they are tucked safely in the middle right after the verb, letting bardzo szybko take the final spot.

What exactly does je refer to here?

je is the Accusative plural pronoun for non-masculine-personal nouns, meaning "them". In the context of a tailor, it likely refers to plural items of clothing like spodnie (trousers) or koszule (shirts). If the tailor were sewing a single masculine object like a suit (garnitur), the pronoun would change to go.

Why use uszyje instead of będzie szył?

uszyje is a perfective verb, which means it focuses on the completed result: the tailor will completely finish making the clothes. If you used the imperfective będzie szył, it would mean "will be sewing" and focus only on the ongoing process, without emphasizing that the job gets finished.