Learn Polish: Helikopter odleciał od szpitala bardzo szybko. - The helicopter flew away from the hospital very quickly.

The base verb lecieć means to fly. Adding the prefix od- creates odlecieć, which specifically means to fly away or to depart. It also makes the verb perfective, meaning the action of flying away is viewed as a single, completed event.

Why do we see od twice, once in odleciał and again right after it?

This is a very common Polish pattern! When a verb of motion has a prefix showing direction, the preposition that follows often matches it. The prefix od- (away) pairs perfectly with the preposition od (from) to strongly emphasize the separation from a starting point.

Why is the word for hospital in the form szpitala?

The preposition od always requires the noun following it to be in the Genitive case. For the masculine inanimate noun szpital, the Genitive ending is -a, making it szpitala.

Why use the adverb szybko instead of the adjective szybki?

You are describing how the helicopter flew (modifying the verb odleciał), so you need the adverb szybko (quickly). If you wanted to describe the noun itself, like saying The fast helicopter flew away, you would use the adjective: Szybki helikopter odleciał.