"Lentamente" (Slowly) is a slow-burn flirtation song, and it does not pretend to be anything else. The narrator walks up to a woman "como si nada" (as if it were nothing), and she stays cool, but they are both curious. She wonders whether they have "compatibilidad en la cama" (compatibility in bed). He offers her a drink first, "pero sin hielo" (but without ice), and soon "la niña ya coge vuelo" (the girl is taking off). Coger vuelo literally means to take flight, here it means she is getting carried away.
The chorus is where the title comes from: "Lentamente, se pone caliente" (slowly, she heats up). She bites her lips, clenches her teeth, and "su cara no miente" (her face doesn't lie). The hook "Se va, se va, se va, con un besito nada más" (she's going, going, gone, with just one little kiss) is the most catchy part. In the second verse the Spanish gets mixed with English the way reggaeton loves to do: "me gusta tu body", "tus stories", "nos vamos a la glory". It is fun to spot how much Spanglish is in there.