wǒmen zǒu lóutī shànglóu, bú zuò diàntī.

They do relate to the same action, but they focus on different parts of it.

• 走楼梯 = take the stairs / go by the stairs
• 上楼 = go upstairs

So together, 走楼梯上楼 means something like:

go upstairs by taking the stairs

The first part tells you how you go, and the second part tells you where/direction you go.

Yes, you can, but the meaning changes slightly.

• 我们上楼，不坐电梯 = We’re going upstairs, not taking the elevator.
• 我们走楼梯上楼，不坐电梯 = We’re going upstairs by taking the stairs, not the elevator.

The full sentence is more explicit because it clearly says the stairs are the chosen method.

Here 走 means walk or go on foot.

In 走楼梯, it helps express the idea of taking the stairs. It is not just the basic meaning to walk in isolation; together with 楼梯, it forms a common idea:

• 走楼梯 = use the stairs / take the stairs

So this is more natural than translating word-for-word as walk stairs.

This is because of a tone change rule.

Normally, 不 is fourth tone: bù.
But when 不 comes before another fourth-tone syllable, it changes to second tone: bú.

Here:

• 坐 is fourth tone: zuò
• so 不坐 is pronounced bú zuò

This is only a pronunciation change. The character is still written 不.

Literally, yes, 坐 often means sit, but in Chinese it also commonly means ride / take for transportation or similar means of travel.

So:

• 坐车 = take a car / ride in a vehicle
• 坐飞机 = take a plane
• 坐电梯 = take the elevator

This is a very common extension of the verb 坐.

Mandarin often does not need extra words that English requires.

In English, you might say:

• go upstairs by taking the stairs
• walk up the stairs to go upstairs

In Mandarin, verbs can be placed one after another more directly:

• 走楼梯上楼

This kind of structure is very common. Chinese often links actions and direction without adding separate words like to, by, or in order to, as long as the meaning is clear from context.

Yes. 上楼 is a common verb phrase meaning go upstairs.

It is made of:

• 上 = up / go up
• 楼 = floor / building level

So 上楼 does not just mean up building word-for-word; together it means go up to an upper floor.

Related expressions include:

• 下楼 = go downstairs
• 上车 = get in / get on a vehicle
• 下车 = get out / get off a vehicle

The comma helps separate two contrasting parts:

• 我们走楼梯上楼
• 不坐电梯

This makes the sentence easier to read and emphasizes the contrast:

take the stairs, not the elevator

In spoken Mandarin, you would naturally pause there a little.

Yes, that is also natural.

• 我们走楼梯，不坐电梯 = We take the stairs, not the elevator.
• 我们走楼梯上楼，不坐电梯 = We take the stairs upstairs, not the elevator.

The version with 上楼 is more specific because it tells you the direction: upstairs.

Without 上楼, the sentence is still fine if the situation already makes it obvious.

Mandarin usually does not use articles like a, an, or the.

So:

• 楼梯 can mean stairs / the stairs
• 电梯 can mean elevator / the elevator

The exact meaning depends on context.

Chinese also does not need a measure word here because 楼梯 and 电梯 are being used directly as objects of the verbs 走 and 坐. Measure words are mainly needed when counting or specifying:

• 一部电梯 = one elevator
• 一个楼梯口 = one stair entrance

It can be omitted if the subject is already understood.

• 我们走楼梯上楼，不坐电梯。 = explicit: We take the stairs upstairs, not the elevator.
• 走楼梯上楼，不坐电梯。 = more general or context-based: Take the stairs upstairs, don’t take the elevator or (We) take the stairs upstairs, not the elevator, depending on context.

Mandarin often drops subjects when they are obvious from the situation.