How to say goodbye in Mandarin Chinese

 再见 zàijiàn see you again

拜拜 bàibai bye bye

Time phrase + 见

明天见 see you tomorrow

下次见 see you next time

周一见 zhōuyī jiàn see you on Monday

先走了xiān zǒu Le 

晚安 good night

一会见 yí huìr jiàn

待会儿见 dāi huìr jiàn 

保重