Learn Italian: C'è un incendio, ma l'ambulanza sta per arrivare. - There is a fire, but the ambulance is about to arrive.

This sentence uses the structure stare per + an infinitive verb, which is how Italians express that an action is imminent or "about to" happen. Since the ambulance (l'ambulanza) is an "it", we use the third-person singular form sta, followed by per, and then the action in its dictionary form: arrivare.

Could I use fuoco instead of incendio for "fire" here?

Not in this context! While fuoco translates to "fire" generally (like a campfire or a stove), incendio specifically means an uncontrolled, dangerous emergency fire (like a house fire or wildfire). Since an ambulance is coming, we know it's an emergency, making incendio the right word.

If there were multiple ambulances, how would the stare per phrase change?

Only the verb stare changes to match the new plural subject. The phrase would become le ambulanze stanno per arrivare. The word per and the infinitive verb (arrivare) stay exactly the same no matter who or what is about to do the action.

Just as a quick refresher, why do we use c'è instead of just è at the beginning?