How many languages does Oliver Queen speak in the Arrow?
Oliver Queen has been shown to be fluent in multiple languages. From the Arrowverse Wikia:
Multilingual: Oliver is capable of fluently speaking English, Russian, Cantonese, Mandarin, Japanese, Spanish, and Arabic. He can speak Mandarin so perfectly that a blinded Chinese Triad member believed Oliver was actually Chinese.
He learned Arabic through the League of Assassins. Cantonese, Mandarin, Japanese while stuck in Hong Kong. Russian during his time with Solntsevskaya Bratva, a group part of the Russian mafia. English from birth. It hasn't been shown where he learned Spanish from or when.