I am a beginner Korean learner so I don't know how natural these sound but here are some resources # "i need to do something now" See https://www.howtostudykorean.com/unit-2-lower-intermediate-korean-grammar/unit-2-lessons-42-50/lesson-46/#463 # "don't stay up too late" Someone had the same question on HiNative. It also seems to be basically the same as what Naver Papago translate gives, https://papago.naver.com/?sk=auto&tk=ko&st=Don%25%2339t%20stay%20up%20too%20late > 너무 늦게까지 일어나 있지 마요 > > -- Sweeee36, https://hinative.com/en-US/questions/2173485 너무 -> very 늦게 -> late (adverb, ~게), https://www.howtostudykorean.com/unit1/unit-1-lessons-1-8/unit-1-lesson-8/#degree 까지 -> until, https://www.howtostudykorean.com/unit1/unit-1-lessons-9-16/lesson-12/#kp4 일어나 있지 마요 -> don't stay up Related questions - https://hinative.com/en-US/questions/2173485 - https://www.italki.com/question/363039 - https://hinative.com/en-US/questions/1608890 - https://hinative.com/en-US/questions/2485042 Here are some other notes, 늦다 -> to be late 일어나다 -> to get up 깨다 -> to wake (up) 일찍 자세요 -> Please go to bed(sleep) early <verb>지 마세요 -> Please don't <verb>

"Don't stay up too late" is fine. As for "I need to do something now." I would say "I need to go and do something now." Or "I have something that I need to do now" Just saying "I need to do something now" makes it sound like you're so bored that you have to do something to alleviate the boredom.