Thang máy ở chung cư đang bị hỏng, vì vậy mọi người phải đi cầu thang.

Here ở means at / in and links the noun thang máy with its location chung cư.

So thang máy ở chung cư means the elevator in the apartment building / apartment complex.

A very literal breakdown is:

• thang máy = elevator
• ở = at, in
• chung cư = apartment building / apartment complex

Vietnamese often uses ở after a noun to show where that thing is located.

Chung cư usually means an apartment building, apartment block, or sometimes condominium building, depending on context.

In this sentence, it refers to the residential building where the elevator is. So ở chung cư is naturally understood as in the apartment building or at the apartment complex.

It does not usually mean a single apartment unit. It refers more to the building or housing complex.

Both are possible, but they are slightly different in feel.

• hỏng = broken, out of order
• đang hỏng = currently broken / in a broken state now
• đang bị hỏng = is currently broken, with a slightly stronger sense that it has suffered a problem or is in an unfortunate state

In everyday Vietnamese, bị often adds an adversely affected nuance. It is very common with unpleasant situations:

• bị ốm = to get sick
• bị mất điện = to have a power outage
• bị hỏng = to be broken

So đang bị hỏng sounds very natural for is currently out of order.

Đang marks an action or state as ongoing at the present time.

In this sentence, it tells you the broken condition is true right now:

• thang máy hỏng = the elevator is broken
• thang máy đang hỏng = the elevator is broken right now / currently out of order

Even though English may not always use currently, Vietnamese often uses đang to emphasize the present situation.

Not exactly. Bị often overlaps with passive meaning, but it is broader than that.

It commonly shows that the subject is affected by something negative or unwanted. So it can feel like:

• passive
• adverse result
• unfortunate situation

For example:

• Xe bị hỏng = The vehicle is broken / The vehicle has broken down
• Anh ấy bị mất ví = He lost his wallet / He had his wallet stolen
• Tôi bị đau đầu = I have a headache

So in this sentence, bị hỏng is not just grammar; it also suggests an undesirable condition.

Vì vậy means therefore, so, or for that reason. It links the first clause to the consequence in the second clause.

Structure:

• problem: Thang máy ở chung cư đang bị hỏng
• result: vì vậy mọi người phải đi cầu thang

So it clearly marks cause and effect.

Other common connectors with a similar meaning are:

• nên = so
• cho nên = therefore / so
• vì thế = therefore / because of that

Vì vậy sounds a bit more formal or neatly connected than plain nên, but it is still very normal.

Yes. A very natural alternative would be:

Thang máy ở chung cư đang bị hỏng, nên mọi người phải đi cầu thang.

This means the same thing.

Very roughly:

• nên = so
• vì vậy = therefore / because of that

In conversation, nên is often a little simpler and more common. Vì vậy sounds slightly more explicit or formal.

Here mọi người means everyone or everybody in the situation.

It refers to the residents or people there who are affected by the broken elevator.

Depending on context, mọi người can mean:

• everyone
• everybody
• all the people present

It is very common in everyday Vietnamese.

Note that người ta would be different; that often means people in general or they in an unspecified sense.

Phải is a modal verb meaning must / have to, so it comes before the main verb:

• phải đi = must go
• phải làm = must do
• phải chờ = must wait

So:

• mọi người phải đi cầu thang = everyone has to use the stairs

This is the normal Vietnamese word order:
subject + modal + main verb

Yes, literally it may look strange to an English speaker. In Vietnamese, đi cầu thang means go by the stairs or use the stairs.

The verb đi is very flexible. It can mean:

• go
• walk
• travel
• use a route

So đi cầu thang is a natural way to say that people must take the stairs.

English prefers take the stairs or use the stairs, but Vietnamese uses đi very naturally here.

These two words are easy to confuse because they both contain thang, but they are different:

• thang máy = elevator / lift
• cầu thang = staircase / stairs

A helpful way to remember them:

• máy means machine, so thang máy is the machine stairs → elevator
• cầu thang refers to the actual staircase structure

So the sentence contrasts the two: the elevator is broken, so people must use the stairs.

Yes, but the nuance changes.

• đi cầu thang = use the stairs; neutral and general
• leo cầu thang = climb the stairs; emphasizes the physical act of climbing upward

In this sentence, đi cầu thang is more neutral and natural because it simply contrasts with using the elevator.

If you wanted to stress the effort, you could say:

...mọi người phải leo cầu thang.

That sounds more like everyone has to climb the stairs.

Yes. The subject is the whole noun phrase:

thang máy ở chung cư = the elevator in the apartment building

Then the predicate is:

đang bị hỏng = is currently broken

So the structure is:

• [Subject] thang máy ở chung cư
• [Predicate] đang bị hỏng

Then the second clause:

• [Connector] vì vậy
• [Subject] mọi người
• [Predicate] phải đi cầu thang

Vietnamese does not have articles like English the and a/an.

Whether something is definite or indefinite is usually understood from context.

So:

• thang máy can mean an elevator or the elevator
• chung cư can mean an apartment building or the apartment building
• cầu thang can mean stairs / the stairs

In this sentence, context makes everything definite enough: we are talking about the elevator in that apartment building and the stairs people must use there.

Yes, it is natural and correct. A native speaker might also say it in a few other ways, such as:

• Thang máy ở chung cư bị hỏng, nên mọi người phải đi cầu thang.
• Thang máy chung cư đang hỏng, vì vậy mọi người phải đi cầu thang bộ.
• Thang máy bị hỏng, nên mọi người phải dùng cầu thang.

Small differences:

• removing đang makes it slightly less focused on right now
• thang bộ specifically means the stairs / stairway
• dùng cầu thang means use the stairs

But your original sentence is perfectly natural.

Cầu thang bộ specifically means the staircase used for walking, especially when contrasting it with an elevator.

• cầu thang = stairs / staircase
• cầu thang bộ = stairs (as opposed to the elevator), stairway for walking

In many contexts, cầu thang is enough. But in buildings, especially when contrasting with thang máy, you may hear cầu thang bộ.

So these are both natural:

• phải đi cầu thang
• phải đi cầu thang bộ

The second one is a bit more specific.

Yes. By itself, đi cầu thang just means use the stairs. It does not specify direction.

If you want to be specific, Vietnamese can say:

• đi lên bằng cầu thang = go up by the stairs
• đi xuống bằng cầu thang = go down by the stairs
• leo cầu thang = climb the stairs, usually upward
• xuống cầu thang = go down the stairs

In your sentence, the exact direction does not matter, so đi cầu thang is enough.

Yes, the comma is helpful because it separates two clauses:

1. Thang máy ở chung cư đang bị hỏng
2. vì vậy mọi người phải đi cầu thang

It works much like a pause before therefore or so in English.

Vietnamese punctuation is often flexible in informal writing, but here the comma makes the cause-and-result structure clearer and more natural.