"nice to meet you"
there are several levels of speech. if it's a formal occassion, people usually say "만나서 반갑습니다" (mannaseo pangkapsemnida). you can use this if you meet an elder person or those of upper rank in social status or you just want to make the situation formal.
for casual occassion, especially among youngsters, it's fine only saying "반가워요" (pangkawoyo).
"what are you doing now"
there are some variations. the most casual is "지금 뭐 해요?" (jigeum mwo haeyo? )or "지금 뭐 하고 있어요?" (jigeum mwo hago isseoyo?). you can also go with honorific pattern by using honorific suffix like "-ㅂ니까" or adjust a bit to a polite style using suffix "(으)세요"