Mi Universo Entero is a love song that starts with a guy waking up and staring at a photo on his phone. He looks at "tu sonrisa y tu bello rostro" (your smile and your beautiful face) and admits it makes him feel like a fool: "me vuelvo loco, me siento un tonto" (I go crazy, I feel like an idiot). The big line is the hook, "tú eres mi universo entero" (you are my whole universe), and it is about as sweet as it sounds.
What makes it fun is how ordinary the romance is. He loves "grabar videos, tomarnos fotos y perrear lento" (recording videos, taking photos and dancing slow and close; perrear is to dance reggaeton-style). Then there is "salir de peda", Mexican slang for going out partying, and getting ebrios (drunk). Later he remembers singing in the car together and promises "en tus días más tristes seré tu abrigo" (on your saddest days I'll be your coat), a lovely way to say he will keep her warm and safe. By the end he just wants to grow old with her, and "no te cambio por nada" (I wouldn't trade you for anything).