Questions & Answers about A propos, widziałeś ten nowy film?
Why is a propos spelled this way, and how is it pronounced?
It is a loanword borrowed directly from French, meaning "by the way" or "speaking of which." Just like in French, the final "s" is silent in Polish, so you pronounce it as "a propo".
Why use the imperfective widziałeś instead of the perfective zobaczyłeś for "have you seen"?
When asking if someone has the general experience of having seen a movie, play, or exhibition, Polish typically uses the imperfective aspect (widzieć). It focuses on the experience itself. The perfective (zobaczyć) would sound more like asking if you managed to catch sight of it at one specific, completed moment.
ten nowy film is the direct object here. Why don't the word endings change?
The phrase is in the accusative case because it is a direct object, but it looks identical to the basic dictionary form (nominative). This happens because film is a masculine inanimate noun. For masculine inanimate nouns and their describing words, the accusative form is always exactly the same as the nominative.
How would this sentence change if I were asking a female friend?
You would change the verb to widziałaś. The past tense ending -eś in widziałeś indicates that you are addressing a male, while -aś is used for addressing a female. The rest of the sentence remains exactly the same.