Learn Italian: Il direttore dell'albergo è sempre indisponibile per i clienti. - The hotel manager is always unavailable for the clients.

It uses the negative prefix in- added to the adjective disponibile (available). Just like in English, adding in- creates the exact opposite meaning, turning it into indisponibile (unavailable).

Why do we use dell'albergo instead of just di albergo?

Because you are talking about a specific hotel's manager, you must include the definite article. Since albergo starts with a vowel, it takes the article l'. Combining the preposition di (of) with l' creates the combined word dell'.

What is the difference between albergo and hotel in Italian?

There is no difference in meaning. Albergo is the traditional Italian word, while hotel is a borrowed word that Italians use just as frequently. You can use them interchangeably.

Could direttore also mean a movie director?

No, a movie director is called a regista. The word direttore is used for the manager or head of a business, institution, bank, or in this case, a hotel.