1. 同楼上 “我喜欢音乐。那你呢？你喜欢吗？” "i like music,what about you? do you like it?" 2. 那 你怎么办？ "So, what can you do?" 3. Maybe you mean “なに”, or "纳尼" in Chinese... It's actually a Japanese word, which means "What!?". It's often used by young Chinese people who watch Japanese anime a lot. "你的答案错了" “纳尼!?” "Your answer is wrong." "What!?"

另一个例子 我很喜歡中國菜， 那你？？ I like Chinese food very much ,and you ? (what about you ?) 我也！me too !

”那你呢“？ = Then what about you? ”那我们走吧。“ = Then let's go. 那basically means "then" I guess. It has no sinificant meaning but to make the sentence more natural.

For example. 女：你喜欢我不？ 男：不喜欢。 女：那 你去死吧

I think it means "and you?".