Take something short and famous in Polish and translate it into English.
Some examples could be a saying, a phrase, a proverb, a children's song or poem, a line from a famous speech, some other famous quotation, or a famous first line from a book.
Writing and speaking are intertwined. In fact, writing is like speaking, just... written (ok, not literally, but you can think of it as a monologue). It's not helpful to translate when speaking and not helpful to do so when writing something. I don't think that watching a movie and translating the lines mentally into your mother tongue is helpful, and neither is translating when writing. That's my opinion.
(Also, I don't know who downvoted your comment, I just upvoted it to keep the balance.)