De a de veras is a colloquial phrase, particularly common in Mexico, that means "truly" or "for real". It's a way to add strong emphasis and sincerity to a statement, much like saying "I'm not kidding" in English.
In the song, the singer laments, "¿Por qué me pagas así? Si yo te quise de a de veras" (Why do you treat me this way? When I loved you for real). This phrase powerfully conveys the depth and genuineness of his feelings, making the heartbreak he sings about feel even more profound and unjust.
Ever had your heart broken so badly that you wished you could travel back in time just to stand someone up? That is the exact mood Grupo Frontera and Maluma bring to "POR QUÉ SERÁ". Right from the start, they hit you with the brutally honest line: "Quisiera volver al día en que nos conocimos / Pa' no ir" [I wish I could go back to the day we met / Just so I wouldn't go]. Paired with wanting an imaginary off switch for human emotions ("Quisiera un botón para apagar los sentimientos" [I wish for a button to turn off feelings]), the track lays out the universal frustration of catching feelings for someone who is only playing games.
The chorus hits with a dramatic, almost cursed realization: "Yo nací pa' querer a la que no me quiere" [I was born to love the girl who doesn't love me]. Maluma jumps in with his signature flair, calling the band his parcero (Colombian slang for "close friend" or "buddy"), and asks the big question: "¿Desde cuándo en tu corazón yo ando sobrando?" [Since when am I extra/unwanted in your heart?]. The phrase "ando sobrando" is great everyday Spanish for feeling like a third wheel or simply unwanted where you used to belong. It is a catchy, bitter track for anyone who feels like their love life is just "otro amor que se me rompe en pedazos" [another love that shatters to pieces].