Look at these sentences:
Ferme la porte à clé avant de partir !
Lock the door before leaving!
J'étais malheureux avant de te rencontrer.
I was unhappy before meeting you.
Avant de commencer, il aimerait porter un toast.
Before starting, he'd like to raise a toast.
Notice that to express 'before + -ing' in French, you use avant de followed by the infinitive form of the verb.
Also note that any object or reflexive pronoun is placed between 'de' and the infinitive.
Learn more about these related French grammar topics
Examples and resources
Avant de commencer, il aimerait porter un toast.
Before starting, he'd like to raise a toast.
J'étais malheureux avant de te rencontrer.
I was unhappy before meeting you.
Ferme la porte à clé avant de partir !
Lock the door before leaving!
Elle veut vérifier avant de prendre une décision.
She wants to check before making a decision.
