Learn Hardcore Chinese: hěnduō dàxuéshēng zhōumò zài kāfēiguǎn dǎgōng. - Many college students work part-time at cafés on weekends.

是 is mainly used to link two nouns/pronouns:
- 他是老师。= He is a teacher.
When you describe where someone is or what they do, you generally don’t use 是. You just use:
- Subject + (time) + (place) + verb

So:

很多大学生周末在咖啡馆打工。
Literally: Many college students weekends at cafés work-part-time.

Saying:

✗ 很多大学生周末是，在咖啡馆打工。
✗ 很多大学生周末是在咖啡馆打工。 (in neutral context)

is usually unnecessary or awkward.

是在…打工 can be used, but it adds emphasis to the location, like:

他们不是在图书馆，他们是在咖啡馆打工。
They’re not working in the library; they’re working in the café (emphasis on 在咖啡馆).

Why doesn’t 大学生 have a plural ending like “-s” in English? Why no 大学生们?

Chinese usually doesn’t mark plural on nouns the way English does.

大学生 can mean “college student” or “college students” depending on context.
The word 很多 (“many”) already shows it’s plural, so 大学生 doesn’t need any extra marking.

The suffix 们 is:

Used mainly with pronouns: 我们 (we), 你们 (you all), 他们 (they)
Sometimes with specific, known groups of people: 同学们 (you classmates), 孩子们 (the children)

But you don’t normally put 们 after a noun that already has a number or a quantity word (like 很多):

✗ 很多大学生们 – incorrect / very unnatural
✓ 很多大学生 – correct

Shouldn’t there be a measure word, like 很多个大学生?

With many nouns in Chinese you need a measure word between a number/quantity word and the noun:

一个学生 – one student
三本书 – three books
很多个人 – many people (with 个)

But:

After 很多, it’s very common and natural to omit 个 when the noun is a general category like 学生 / 人 / 问题:
- 很多学生 – many students
- 很多人 – many people
- 很多问题 – many questions
很多大学生 is the most natural form here.
- 很多个大学生 is possible in some contexts, but it sounds more colloquial/emphatic and less standard, and not needed in this neutral sentence.

For learners, treat 很多大学生 as the normal, correct pattern.

Why is there no 的 between 大学 and 生? Why not 大学的学生?

Both exist, but they’re slightly different:

大学生 is a compound word meaning “college student” (a single vocabulary item).
大学的学生 literally means “students of the university.”

In most contexts they are interchangeable, but:

大学生 is shorter and more common as a general category.
大学的学生 can sound slightly more specific or descriptive, e.g. “the students of that university (as opposed to high-school students).”

In this sentence, 很多大学生… is the most natural and idiomatic way to say “many college students.”

Why is 周末 (weekends) in the middle of the sentence? Can it go somewhere else?

The sentence is:

很多大学生周末在咖啡馆打工。

Typical Chinese order is:

Subject + Time + Place + Verb

So 周末 goes between the subject and the place phrase.

You can also move the time phrase to the very beginning for emphasis:

周末，很多大学生在咖啡馆打工。
On weekends, many college students work at cafés.

Both are common and correct. Putting 周末 at the very end:

✗ 很多大学生在咖啡馆打工周末。

is unnatural in Chinese.

Does 周末 here mean “every weekend” or “this weekend”?

By default, 周末 in a sentence like this is general/habitual:

很多大学生周末在咖啡馆打工。
= Many college students (typically) work part-time at cafés on weekends.

If you want to talk about a specific weekend, you usually add a modifier:

这个周末 – this weekend
上个周末 – last weekend
下个周末 – next weekend

Example:

很多大学生这个周末在咖啡馆打工。
Many college students are working at cafés this weekend.

What exactly does 打工 mean? Can I just use 工作 instead?

打工 (dǎgōng) usually means:

To work a part-time, often low-wage or side job
Very commonly used for students working outside class
Also used for migrant workers working for an employer

Examples:

我在咖啡馆打工。– I work part-time in a café.
暑假的时候他去工厂打工。– He went to a factory to do temporary work in the summer vacation.

工作 (gōngzuò) is more general:

To work; a job, career
Often suggests a more formal or regular job.

You can say:

很多大学生周末在咖啡馆工作。

This is grammatically fine, but it may sound more like they work there as their regular job.
Using 打工 fits the idea of part-time student jobs more naturally.

What is the role of 在 in this sentence? Is it like the progressive “-ing” marker?

在 has two common uses that learners meet early:

在 + place = “at / in / on (a place)”
- 我在学校。– I’m at school.
- 他在家。– He’s at home.
- 他们在咖啡馆打工。– They work at the café.
在 + verb phrase = progressive “be doing”
- 我在看书。– I’m reading (right now).
- 他在吃饭。– He’s eating.

In this sentence:

在咖啡馆打工

在 belongs with 咖啡馆, so it is the location marker, not the progressive:

在咖啡馆 = at the café
打工 = work part-time

So the structure is: 在 + [place] + [verb], not 在 + [verb].

Could we say 在周末在咖啡馆打工 with two 在? Is that OK?

Yes, grammatically you can say:

很多大学生在周末在咖啡馆打工。

Here:

在周末 – during the weekend (time phrase)
在咖啡馆 – at the café (place phrase)

However:

In everyday speech and writing, Chinese usually drops 在 before 周末 and just says 周末.
So 很多大学生周末在咖啡馆打工 sounds more natural and concise.

Use:

周末 (no 在) for time in neutral sentences.
在周末 is possible but slightly heavier, and more often used when you want to contrast with other times, e.g.:
- 平时我在学校上课，在周末在咖啡馆打工。
  On weekdays I have classes at school; on weekends I work at a café.

Can I say 在咖啡馆里打工 instead of 在咖啡馆打工?

Yes:

在咖啡馆打工 – work at a café
在咖啡馆里打工 – work inside a café

里 means “inside.” Often:

With buildings like 咖啡馆 / 学校 / 图书馆, adding 里 is optional:
- 我在学校(里)。– I’m at school / in the school.
在咖啡馆打工 is slightly more neutral and is what you’ll hear most often.
在咖啡馆里打工 puts a tiny bit more focus on the inside vs. just “at” the café area, but in practice there is usually no big difference.

How would I turn this sentence into a yes–no question or a negative sentence?

Yes–no question
Add 吗 at the end:
- 很多大学生周末在咖啡馆打工吗？
  Do many college students work part-time at cafés on weekends?
You can answer:
- 是的，很多大学生周末在咖啡馆打工。
- 不是，很多大学生周末不在咖啡馆打工。
Negative sentence
Put 不 before the verb phrase:
- 很多大学生周末不在咖啡馆打工。
  Many college students do not work part-time at cafés on weekends.

You could also move the time to the front:

周末很多大学生不在咖啡馆打工。
On weekends, many college students don’t work at cafés.