to calm down zur Ruhe kommen [Redewendung] [sich entspannen]
to calm down - acalmar-se - https://www.infopedia.pt/dicionarios/ingles-portugues/calm%20down
Sinônimo de acalmar:
tranquilizar, sossegar, serenar, descansar, repousar, aquietar, quietar, apaziguar, abrandar, amainar