Hi Alison, I'm not a native speaker of Korean, but a simple way to say what you want is: 짧게 말할게요. (I'll keep it short) You can add a reason, for example: 다들 바쁘니까 짧게 말할게요 (you are all busy so I will keep it short) 방해해서 미안해요. 짧게 말할게요. (Sorry to disturb you. I'll keep it short) 거두절미하고 짧게 말 하겠습니다 (I'll cut to the chase) By the way, 거두절미 is a lovely 4 word korean phrase to know - it literally means go away (거) head (두) , cut off (절) tail (미) and has the english meaning of "to cut a long story short, to summarize, to get to the point"

formally (meeting, talk to boss) 잠시 보고드릴게 있습니다. 간단히/짧게 말씀드릴게 있습니다. informally (talk to friends) 잠깐 (시간) 괜찮아? 시간 좀 있어?