Fingir means "to pretend" or "to feign." It's an interesting word because it implies a deliberate act of deception or putting on a false front, which is a powerful concept in relationships.
In "Decide Tú," the singer is exhausted from fingir (pretending) to be okay or to be in a different emotional state than he truly is. This word captures the core conflict of the song, where he's tired of living a lie and wants his partner to make a decision about their future.
"Decide Tú" is a confession. The narrator has been unfaithful, and instead of hiding it any longer, he tells his partner the truth and hands the decision to her.
He opens by admitting he can't keep going like this. The guilt is eating at him: he looks at her and immediately regrets what he's done, and he's not sure he can carry the weight of it much longer.
In the chorus he stops making excuses. He's tired of pretending, ashamed of himself, and ready to ask for forgiveness even though he knows he might not get it. He says plainly that he's betrayed her love, and that it's her call now, not his, what happens next.
The song leans into its banda roots with a shoutout to Banda La Sinaloense partway through, a nod to the collaboration behind the track, before the confession returns for one more round.