Arquitecto translates to "architect". It's an interesting word choice in a love song, as it typically refers to someone who designs buildings.
In this song, the singer uses it metaphorically, saying, "Sabiéndome arquitecto de tus días" (Knowing myself to be the architect of your days). This implies he sees himself as the designer and builder of his beloved's happiness and future, making it a unique and powerful expression of devotion.
Antonio Orozco wakes up and can't stop naming things: "Desperté a tu lado, desperté sin aire y desperté" [I woke up by your side, I woke up without air, and I woke up] — the same verb three times in one breath, like he's still catching up with what happened overnight. He never really explains what changed. He just keeps listing it: "Eres una música con alma, eres tierra y eres agua" [You are music with a soul, you are earth and you are water].
By the last chorus he's run out of comparisons and just admits it: "Eres tanto que no sé ni qué decir" [You are so much that I don't even know what to say]. It's an odd way to close a love song — the words giving out right when he needs them most — but it lands, because everything before it was already proof he'd been trying.