Truchas literally translates to 'trouts', but in Mexican slang it is a highly popular way to describe someone who is 'alert', 'sharp', or 'on their toes'.
In the song, Peso Pluma sings "Sigo bien truchas haciendo negocios" (I stay very sharp doing business) to highlight his street smarts and focus. Mastering colorful local slang like this is a fantastic way to sound much more natural and expressive when speaking Spanish.
Peso Pluma kicks off "Rosa Pastel" by telling us he might be young, but he's smart and persistent: "De poco edad, pero bien listo porque la verdad / Siempre persisto para grande llegar" (Young, but very smart because the truth is / I always persist to make it big). The whole song is a story about his hustle in the drug trade, and he's not subtle about it. He talks about being sharp in business, "Sigo bien truchas haciendo negocios" (I'm still sharp doing business), and moving products all the way in Amsterdam. The title itself, "Rosa Pastel" (Pink Pastel), is slang for a specific drug, likely pink cocaine, which he offers up casually: "Ahi va una onza de Rosa Pastel" (There goes an ounce of Pink Pastel).
Throughout the song, he honors his late father, who he calls "el boss que está junto a Dios" (the boss who is with God), and follows the lessons he was taught. He also gives shout-outs to his network, from his godfather to a "titan" he met in the Amazon. What makes the track stand out is how straightforward he is about the logistics. He sings about small planes delivering goods like a supermarket, "Las avionetas llevan el mandado / Como si fueran un supermercado" (The small planes carry the order / As if they were a supermarket). It's a bold look into a dangerous world, told from the perspective of an ambitious young man making his way up.