The most common Korean word for “quickly” is 빨리 (ppalli). There is one more word with a similar meaning — compare them below. 「quickly」는 한국어로 빨리.
quickly; without hesitation; without delay
TOPIK 1 · adverb
Words and levels: TOPIK I essentials (National Institute of Korean Language standard curriculum, KOGL Type 1) · examples: Cheesepotato