“Gomapseumnida” and “Gamsahamnida” — two thank-yous, one English word
One is native Korean, one is Sino-Korean, and the choice is a small signal about distance. Neither is wrong, and most speakers say they do not think about it.
politeness
“Gwaenchanayo” (괜찮아요) — it also means “no thank you”
The subtitle says “It’s okay” and the character has just declined. If someone offers you something and you actually want it, this is the one word not to say.