Learn Polish: Co pan nam dzisiaj proponuje? - What are you proposing to us today?

nam is the dative form of my (we), meaning to us. The verb proponować (to propose or offer) requires the dative case for the person receiving the proposal. You would only use nas if you needed the accusative or genitive case, like if someone was actually offering us as candidates for a job.

The translation says are you proposing, but isn't pan the word for man or sir?

Yes, but pan is also how you say you formally to a man in Polish. Because pan grammatically acts like a third-person noun, the verb proponuje must be in the third-person singular form (he/she/it proposes), rather than the standard second-person you form.

Why is the short pronoun nam placed before the verb rather than at the end?

Polish prefers not to leave short pronouns like nam at the very beginning or the very end of a clause. Placing it safely in the middle of the sentence, tucked right after the subject pan, sounds much more natural to a native speaker.

Could this sentence also translate to What do you propose to us today?

Absolutely. Polish does not have a separate continuous tense like English does. The single verb proponuje translates to both do propose and are proposing. You just use the context of the sentence to decide which sounds better in English.