Learn Farsi: قرار است که آن‌ها خبر نادرست را بررسی کنند. - They are supposed to check the incorrect news.

The word درست (dorost) means correct or right. By attaching the negative prefix نا- (nâ-), it turns into نادرست (nâ-dorost), meaning incorrect. This prefix works just like un- or in- in English to flip an adjective's meaning.

Why is the verb بررسی کنند (barrasi konand) in the subjunctive mood?

The opening phrase قرار است که (gharâr ast ke), meaning it is supposed that or it is arranged that, requires the following verb to be in the subjunctive mood. Because checking the news is an intended plan rather than an established fact, the compound verb بررسی کردن (barrasi kardan) must take the subjunctive form.

Why does the object marker را (râ) come after the adjective instead of the noun خبر (khabar)?

The marker را (râ) must follow the entire specific direct object phrase, not just the noun itself. Because the core noun and its adjective are linked together by the ezafe as خبر نادرست (khabar-e nâ-dorost), the marker goes at the very end of that complete block.

How does قرار است (gharâr ast) work to mean they are supposed to?

Literally, قرار است means the arrangement is or the decision is. Farsi uses this impersonal structure followed by که (ke) and a subjunctive clause to express that someone is supposed to do something. So the literal flow of this sentence is: The arrangement is that they check the incorrect news.