疑问代词

The most important rule about Chinese question words: they do NOT move. Unlike English ('Where are you going?' — 'Where' moved to the front), Chinese keeps the question word exactly where the answer would go.

Compare: 你去学校 (You go to school) → 你去哪儿？(Where are you going?) — the question word 哪儿 replaces 学校 in the same spot. 他是老师 (He is a teacher) → 他是谁？(Who is he?) — 谁 replaces 老师 in the same position.

Main question words at HSK 1: • 谁 (shéi) — who: 谁来了？(Who came?), 你是谁？(Who are you?) • 什么 (shénme) — what: 你吃什么？(What are you eating?), 这是什么？(What is this?) • 哪儿/哪里 (nǎr/nǎlǐ) — where: 你去哪儿？(Where are you going?), 厕所在哪儿？(Where is the restroom?) • 几 (jǐ) — how many (for small numbers, usually ≤10): 你有几个朋友？(How many friends do you have?) • 多少 (duōshǎo) — how many/much (for larger amounts or prices): 多少钱？(How much?), 你们有多少人？(How many of you are there?) • 怎么 (zěnme) — how / why: 你怎么来的？(How did you get here?) • 为什么 (wèishéme) — why: 你为什么不来？(Why didn't you come?)

Do NOT add 吗 when using a question word. The question word itself makes it a question. 你去哪儿吗？ is redundant and unnatural.