Arrego is a colloquial term in Brazilian Portuguese, often meaning a 'truce' or 'surrender', especially in a difficult situation. It implies giving up or asking for a break from a struggle.
In this song, the artist sings, "Tô pedindo arrego ouvindo o cd do Pablo" (I'm asking for a truce/surrender listening to Pablo's CD). He's metaphorically surrendering to his feelings of heartbreak and seeking solace in music, making it a relatable and emotionally charged word.
This song captures the feeling of being newly single after a long relationship and finding it hard to adjust. The singer tries to go out and enjoy the single life, but his moves are "rusty" and he's forgotten the "ABCs of single life" because he was so used to being with his partner.
He finds himself lost in a "crazy world" where the freedom that seems like a lot to others feels like "very little" to him. He's struggling to move on, listening to sad music by artists like Pablo and imagining his ex listening to Marília Mendonça to get over him. He even thinks about escaping to the beach to forget her, but memories of how close they were keep flooding back, and he holds onto the hope that she might still listen to him.