"Corta Edad" is a flex song from Clave Especial, and the title sets the whole thing up: "De corta edad / Llegué por todo y voy por más" (Young in years / I came for everything and I'm going for more). The narrator is young, already winning, and wants you to know nobody can stop him: "A mí no me van a parar" (They're not gonna stop me).
Most of the song is a list of what he has now. A Hemi is a big Chrysler V8 engine, so "una Hemi pa' dar el roll" means a muscle car for cruising around, and his garage holds "un convoy" (a whole convoy) of "toys", which here means cars and expensive gear. There is a quick revenge story too: when he started, people said he wouldn't make it and "se rieron los tres" (the three of them laughed), and now he has left them all behind. Watch the Mexican slang: "aguanté vara" means "I held on, I took the pressure", "las pacas" are bundles of cash, "carnal" is "bro", and "le chingamos bastante" is a crude way of saying "we worked our asses off". By the end he is on the malecón (the seafront boardwalk) with dembow on the stereo, "en modo belicón" (in tough-guy mode). It is pure swagger, and it knows it.