"Hatujambo" combines two words "hatuna" which translates to "we don't have" and "jambo" to mean "any matter" (which is usually in the negative sense) combining the two basically means 'we are fine'
Why does this -jambo require the pronoun "Sisi," but the others can stand alone?
It's used politely when beginning a conversation, but aren't used after. They technically aren't needed.
It's also translated as "how are we?"" - how do we know if it's a statement or a question?
so basically we can use the same word 'hatujambo?' to both ask and answer? since "hatujambo?" can be "how are we?" and also "hatujambo." to be "We're fine"