什么时候 (shen2 me5 shi2 hou4) when (literally: what time)
哪里 (na3 li3) where
什么 (shen2 me) what
为什么 (wei4 shen2 me5) why
哪 (na3) which
You may have noticed that several of these words share characters, such as 哪 and 哪里 or 什么, 为什么, and 什么时候. So it's that much easier to learn since you won't have to learn as many characters as you could have.
Here are a few examples of when you would use these questions:
B knocks on A's door.
A: 谁呀?
A: 你是哪一个朋友?B: 我是小李。
A: 请进!
B: 什么?
A: 我说:请进。
B: 对不起,我听不到。
A: 没问题。
Here is the translation:
A: Who is it?
B: It's me, your friend.
A: Which friend are you?
B: I am Little Li.
A: Please enter!
B: What?
A: I said: please enter.
B: Sorry, I didn't hear you.
A: No problem.
A few new words I introduced in this sentence are 请进 (qing2 jin4) please enter, 听 (ting1) to listen, and 到 (dao4) to arrive. The expression 听不到 translates to "I don't hear you," even though it literally is "listening has not arrived."
Other useful questions to know using the above words are:
厕所在哪里?
(ce4 suo3 zai4 na3 li3)
Where is the restroom?
厕所 means restroom, while 在 means "to be located at" or more simply, "at." It will be very useful when talking about locations and places.
你为什么学中文?
(ni3 wei4 shen2 me5 xue2 zhong1 wen2)
Why are you learning Chinese?
你什么时候吃晚饭?
(ni3 shen2 me5 shi2 hou4 chi1 wan3 fan4)
When do you eat dinner?
Try making your own sentences. The only way to learn a language is to use it. If you get stuck, you now know how to ask for help!