Deshojar literally means "to pluck petals off" a flower, often associated with the game "he loves me, he loves me not." It's a visually rich and somewhat melancholic word.
In the song, Gian Marco sings, "Tú no imaginas cuánto me ha costado deshojar las flores que sembraste aquí a mi lado." He uses this beautiful metaphor to express the painful process of trying to undo or remove the memories and feelings that his past love planted in his life, highlighting the difficulty of moving on.
"Tú No Te Imaginas" circles back to one line the whole song is built on: "De una vez por todas, o regresas o te olvido" [Once and for all, either you come back or I forget you]. Gian Marco opens by blaming both sides at once, "Tu paciencia y mi silencio decidieron terminar" [Your patience and my silence decided to end], as if the relationship wore itself out rather than either of them choosing to leave. Debi Nova takes the second verse and throws the same ultimatum right back, so the song plays less like one person pleading and more like two people who have both stopped blinking first.
What actually lands is the line underneath all the back and forth: "Tú no te imaginas lo que te he querido" [You can't imagine how much I have loved you]. He is not angry, just doing the math on what staying has cost him, and the chorus keeps returning to that same accounting instead of letting either of them move on.