"We spoke about him before."
Translation:Nós falamos sobre ele antes.
"We" can be translated to "A gente" but the rest of the phrase have to be on singular.
I have used 'a gente' before without a problem. In this case, though, it is using the accidental past tense like happens some times when it conjugates for nós. So I'm thinking the sentence would come up wrong if based on 'a gente.'