Based on the level of respect or formality, you can say "Do you dream often?" in Korean in 3 ways:

• Informal: neo-neun ggum-eul jaju gguni? (너는 꿈을 자주 꾸니?)
• Formal: dansin-eun ggum-eul jaju ggumnigga? (당신은 꿈을 자주 꿉니까?)당신은 꿈을 자주 꾸십니까?
• Very Formal: dansin-ggeseo-neun ggum-eul jaju ggusipnigga? (당신께서는 꿈을 자주 꾸십니까?)

- you (subjective): neo (너), neo-neun (너는), dangsin-eun (당신은), dansin-ggeseo-neun (당신께서는)
- to dream: ggum-eul gguda (꿈을꾸다)
- often: jaju (자주), jongjong (종종)

Please refer to How to pronounce Korean Alphabet for the English pronunciation in this answer.