Les devoirs = homework.

Avant de = before (in time, not place. "Before" for a place would be "devant." Notice that avant takes de before an infinitive, but would not take it before a noun ("avant le soir," "before the evening.")

Dorment = sleep (third person plural, present tense of the irregular verb dormir).

Tard = late.

Pendant les vacances = during vacation.

Se coucher = to go to bed.

De bonne heure = early, at an early hour.

En semaine = during the week.