Learn Farsi: مگر مرد دیوانه در حیاط غش نکرد؟ - Wait, didn't the crazy man faint in the yard?

Adding magar at the beginning turns it into a question of surprise or disbelief. Instead of just asking for a fact, it translates closer to 'Wait, didn't he faint? I thought he did!' It shows the speaker's expectation was challenged.

Does magar always have to be paired with a negative verb like nakard?

Not always, but it is a very common pattern! When magar is paired with a negative verb, it usually means 'Wait, didn't [X] happen?' If you use it with a positive verb, it often implies disbelief that something actually is happening, like 'Don't tell me he fainted?!'

How is the verb 'to faint' formed in this sentence?

The verb is ghash kardan, which is a compound verb. Like most compound verbs in Farsi, only the helping verb (kardan) takes the tense and negative markers. The noun ghash stays exactly the same, while the third-person past tense kard gets the negative prefix na- to become nakard.

Why is there an -e sound connecting mard and divāneh?