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 

Greetings in Mandarin Chinese


Standard greetings
你好 nǐhǎo hello 
您好 nínhǎo hello (polite)
大家好 dàjiā hǎo hello everyone
早上好 zǎoshàng hǎo good morning
吃了吗 chī Le ma ? Have you eaten?
吃饭了吗? chī fàn Le ma have you eaten
Have you eaten


Casual greatings
哈喽 hālou hi
嗨 hai hi
嘿 hèi what's up

Special Greetings
在吗 zài ma are you there
好久不见 hǎo jǐo bú jiàn long time no see
最近怎么样 zuǐ jìn zěn me yàng how's it going

你哦好吗 nǐ hǎu ma ? How are you
我很好 wǒ hěn hǎu I'm very good
不客气  bù kèqì you're welcome
不用谢 bú yòng xiè you're welcome
再见 zài jiàn goodbye

谢谢 xièxie thank you
拜拜 báibái bye bye