Greetings!
The most common way to greet people in Chinese
What is: 你好！Nǐhǎo!
Asking a friend what he/she would like to drink
What is: 你喝什么？Nǐ hē shénme?
What is 可以 kěyǐ
You want to express your thankfulness
What is: 谢谢！Xièxie!
谢谢你！Xièxie nǐ!
The way to greet more than one person in Chinese
What is: 你们好！Nǐmen hǎo!
Asking a friend if he/she would like to drink tea
What is: 你喝茶吗？
Nǐ hē chá ma?
The word of "come in/enter" in Chinese
What is: 进来 jìn lái
You want to invite your guest to take a seat
What is: 请坐！
Qǐng zuò!
If you want to greet your teacher particularly
What is: 老师好！Lǎoshī hǎo!
What is: 来一杯咖啡
Lái yìbēi kāfēi.
You are late for the class, you need to say:
What is: (我)可以进来吗？
(Wǒ) Kěyǐ jìnlái ma?
You want to respond to "Thank you!"
What is: 不客气！Bú kèqi!
To greet a friend by asking if he/her is busy, and your friend responds to that greeting
What is: 你忙吗？Nǐ máng ma?
我很忙。Wǒ hěn máng.
我不忙。Wǒ bù máng.
You want to offer your friend to drink some coke.
What is: 请喝可乐。
Qǐng hē kělè.
If your teacher and classmates are nice, they would invite you to come in by saying
What is: 请进！Qǐng jìn!
You want to introduce your name in two ways
What is:
我叫... Wǒ jiào ...
我是... Wǒ shì...
What is:
你好吗？Nǐ hǎo ma?
我很好。你呢？Wǒ hěn hǎo. Nǐ ne?
我也很好。Wǒ yě hěn hǎo.
You offer your friend to drink some coffee, but your friend doesn't drink coffee. He/she wants to have some tea.
What is:
请喝咖啡。Qǐng hē kāfēi.
我不喝咖啡。Wǒ bù hē kāfēi.
(你喝什么？Nǐ hē shénme?)
我喝茶。Wǒ hē chá.
If your teacher and classmate are very serious about speaking the full sentence, they would say: You may come in.
What is: 你可以进来。
Nǐ kěyǐ jìnlái.
You want to say Goodbye to your friends
What is: 再见！Zàijiàn!