Learn Polish: Jeśli intencja jest niejasna, nie wiadomo, co zrobić. - If the intention is unclear, it is unknown what to do.

The impersonal predicate nie wiadomo translates to 'it is unknown' or 'one does not know'. When followed by a question word like co and an infinitive like zrobić, it expresses uncertainty about an action. In this context, the structure translates naturally to 'nobody knows what to do'.

Could I use the imperfective robić instead of the perfective zrobić here?

Yes, but the perfective zrobić is a better fit for this sentence. It focuses on taking and completing a specific, one-time action ('what to do to resolve this specific situation'). Using the imperfective robić would imply a more general, ongoing dilemma ('what one should be doing' in a broader sense).

Why is there a comma before co zrobić?

Polish punctuation is heavily based on syntax rather than pauses. You must always place a comma before an infinitive phrase or subordinate clause introduced by a question word like co, gdzie, or jak, no matter how short the phrase is.

Why is niejasna written as a single word?

In Polish, the negative particle nie is written together as a single word with adjectives in their basic, positive degree. Therefore, instead of writing them separately, 'not clear' becomes the single adjective niejasna.