Yo No Entiendo (I Don't Understand) is Diferente Nivel shrugging at the people who can't stand seeing him do well. It opens with old friends who turned their backs now showing up with a friendly "¿qué onda, carnal?" (what's up, bro?). In Mexican slang a carnal is a brother or close buddy, which makes the greeting a little ironic here: his answer is "conmigo no pueden contar" (you can't count on me).
The song is full of plain, blunt life lessons. Some friends are only around while you're doing fine, and "la amistad se les acaba" (their friendship runs out) the moment you're broke. He's proud that "nadie me ha dado de comer" (nobody has fed me), meaning he made it on his own, and he credits his dad: "desde plebe me juntaba con mi apá" (since I was a kid I hung out with my dad). Plebe is northern Mexican slang for a kid, and apá is a casual papá. Pistear means to have a few drinks, which he plans to do with a brass banda playing.
My favorite line is the most modern one: if his trips annoy you, "en el celular te da la opción de silenciar" (your phone gives you the option to mute). It's a very funny way to say mind your own business, and the last line says it outright: "cada quien su vida" (everyone lives their own life).