Learn Italian: Durante il viaggio ho dormito.

Verbs in Italian take either avere (to have) or essere (to be) in the past tense (passato prossimo). While piacere is a special verb that always uses essere (like è piaciuto), dormire (to sleep) is a regular verb that uses avere. So you say ho dormito (I have slept), just like in English.

Why isn't there a preposition like di after durante?

Unlike time words such as prima (before) or dopo (after), which usually need di before a noun (e.g., prima del viaggio), durante (during) doesn't need an extra preposition. You just put the noun directly after it: durante il viaggio.

Why use the passato prossimo (ho dormito) here instead of the imperfetto (dormivo)?

Using ho dormito states a completed fact: you slept for that block of time. If you used the imperfetto (dormivo), it would mean 'I was sleeping,' which usually implies you are setting the scene for something else to happen, like 'I was sleeping when the phone rang.'

Does viaggio only mean 'trip'?