Learn Farsi: ما باید بدون او درباره‌اش صحبت کنیم تا او را در جشن غافلگیر کنیم. - We must talk about it without him to surprise him at the celebration.

It means 'about it' (or 'about him'). It combines the compound preposition درباره (about) with the attached pronoun اش (it). Because درباره ends in a silent 'e' sound, a connecting 'y' sound is added between them, making it dar bâre-y-ash.

Why does the sentence use the attached pronoun in درباره‌اش (about it) but an independent pronoun in بدون او (without him)?

Both ways are grammatically correct! You can use attached pronouns on prepositions (like درباره‌اش and بدونش) or independent pronouns linked with an ezafe (like درباره او and بدون او). Mixing them here avoids repetition and makes the sentence flow nicely, while the independent pronoun او adds a little more emphasis to 'without him'.

Why are both verbs in this sentence (صحبت کنیم and غافلگیر کنیم) in the subjunctive form?

The first verb, صحبت کنیم (we talk), is subjunctive because it follows باید (must). The second verb, غافلگیر کنیم (we surprise), is subjunctive because it follows تا (so that). Both of these trigger the subjunctive because they express a requirement or an intention rather than a stated fact.

What does the word را (râ) do in the phrase او را (u râ)?

The word را is the specific direct object marker in Farsi. Since (him) is a specific, known person receiving the action of being surprised, must immediately follow it to show he is the direct object of the verb .