Quan l'ascensor arriba tard, pugem per l'escala.

Quan means when.

In this sentence, it introduces a time clause:

• Quan l'ascensor arriba tard = When the elevator is late / slow to arrive

Catalan often uses quan just like English when to talk about something that happens regularly or whenever a situation occurs.

Because Catalan articles are often shortened before a vowel.

• el
  • ascensor → l'ascensor
• la
  • escala → l'escala

This is called elision. It works a lot like how in some languages words contract to sound smoother.

So:

• l'ascensor = the elevator
• l'escala = the staircase / the stairs

Literally, it means arrives late.

• arriba = arrives
• tard = late

So l'ascensor arriba tard is literally the elevator arrives late.

In natural English, depending on context, you might also understand it as:

• the elevator is slow
• the elevator takes a long time
• the elevator is late arriving

Catalan uses arribar tard very naturally in this kind of idea.

Because Catalan expresses this idea with the verb arribar (to arrive), not with estar.

So:

• arriba tard = arrives late
• not està tard

This is similar to English: we say it arrives late, not usually it is late when we focus on the act of arriving.

Pugem is from the verb pujar, which means to go up or to climb.

Here, pugem means:

• we go up
• or more naturally in English here, we take the stairs up

So the second part:

• pugem per l'escala

literally means:

• we go up by the staircase

A natural English translation is:

• we go up the stairs
• we take the stairs

Because Catalan usually leaves out subject pronouns when the verb already makes the subject clear.

• pugem already means we go up
• so nosaltres pugem is possible, but usually unnecessary

Catalan does this much more than English.

Compare:

• Pugem = We go up
• Nosaltres pugem = We go up (with extra emphasis, like we do)

Here per means something like by, via, or through.

So:

• pugem per l'escala = we go up by the staircase

In natural English, this often becomes:

• we take the stairs
• we go up the stairs

Catalan often uses per to show the route or means by which something happens.

That is just a difference between the languages.

In Catalan, escala can mean:

• staircase
• stairs

So even though English often uses the plural stairs, Catalan can use the singular l'escala.

You may also hear les escales in other contexts, but per l'escala is perfectly natural.

It most naturally sounds like a general habit or a whenever this happens situation.

• Quan l'ascensor arriba tard, pugem per l'escala.
• When the elevator is late, we take the stairs.

Both verbs are in the present tense, which in Catalan often expresses:

• habitual actions
• general truths
• repeated situations

If you wanted a single past event, the sentence would be different.

Because Catalan, like English, often uses the present tense for repeated or habitual situations.

Here:

• arriba = arrives
• pugem = we go up

Together they describe what usually happens:

• When the elevator is late, we take the stairs.

This is not necessarily happening right now; it is a regular pattern.

Yes. Catalan can also put the main clause first:

• Pugem per l'escala quan l'ascensor arriba tard.

That means the same thing:
We take the stairs when the elevator is late.

Starting with quan... is very natural when you want to set up the condition or circumstance first.

Because the sentence begins with a subordinate clause:

• Quan l'ascensor arriba tard, ...

The comma separates that opening clause from the main clause:

• pugem per l'escala

This is very similar to English:

• When the elevator is late, we take the stairs.

Yes, literally pujar can mean to climb or to go up.

But in this sentence, the most natural English translation is usually:

• we take the stairs
• we go up the stairs

If you say we climb the stairs, it is understandable, but it sounds a bit more physical or deliberate in English than the Catalan sentence usually does.

A simple approximate pronunciation is:

kwan las-sən-SOR ar-REE-bə TART, poo-JEM per ləs-KA-lə

A few helpful notes:

• quan sounds roughly like kwan
• ascensor has stress on the last syllable: -sor
• arriba has stress on ri
• pugem has stress on the second syllable: -gem
• escala has stress on ca

Pronunciation varies somewhat by region, but this will help you get close.

Yes. Ascensor is the standard Catalan word for elevator or lift.

So:

• l'ascensor = the elevator / the lift

Depending on whether you speak American or British English, you might translate it as:

• elevator
• lift

Both are fine.