Depre is a colloquial, shortened form of depresión, meaning "depression". It's a common slang term in Spanish, similar to how English speakers might say "feeling blue" or "the blues" instead of the more formal "depression".
In the song, the artist sings, "De esta depre no veo la salida" (From this depre I don't see the way out). This use of depre makes the lyrics feel more authentic and relatable, capturing a raw, everyday expression of sadness and hopelessness.
"Qué Andas Haciendo" is Carín León and Ke Personajes turning a hangover into a question they can't stop asking. The whole song circles back to one line, "¿Qué andas haciendo" [What are you up to], repeated like he's dialing the same number and getting no answer. He counts the damage instead of hiding it, "Tres noches bebiendo y las que me faltan" [Three nights drinking, and there's more still to come], and admits flat out that "De esta depre no veo la salida" [I can't find a way out of this depression]. There's no plan to fix any of it, just a running tally of how much she took with her when she left.
Then the song does something a little mean to itself. Right after that low point it throws in "Goce y baile, ¿ok?" [Have fun and dance, okay?], a line aimed at her like a dare dressed up as permission. It's the moment the track admits this was never really about getting over anyone. It's about staying up one more night, drink in hand, refusing to be the one who moves on first.