Tôi đang ở tầng một; bạn đến bằng thang máy hay đi cầu thang?

Yes, Tôi ở tầng một is perfectly grammatical and natural.

đang adds the idea of right now / currently. In this sentence, it emphasizes your current location at this moment.

• Tôi ở tầng một = I’m on the first floor / I’m on the first floor in general.
• Tôi đang ở tầng một = I’m on the first floor right now.

So đang is not required, but it makes the situation feel more immediate.

Yes. It is normal.

• ở means to be at / stay at / live at
• đang marks something as ongoing or currently true

So đang ở means currently being/staying at a place.

Learners often first meet đang with action verbs, but it can also be used with location/state verbs like ở when the speaker wants to stress the present situation.

Not always in the way English speakers expect.

This is one of those tricky floor-numbering issues:

• In many Vietnamese contexts, tầng trệt = ground floor
• Then tầng một = the floor above that

But in some buildings, signage may label the ground level as tầng 1. So real-life usage can vary.

That means tầng một can sometimes create confusion if you are thinking in British English vs American English vs local building labels. In real situations, it is smart to check the building’s numbering system.

Because hay is the usual word for or in a question that gives a choice.

• A hay B? = A or B?

So:

• bạn đến bằng thang máy hay đi cầu thang? = Are you coming by elevator or taking the stairs?

By contrast, hoặc is more common in statements, lists, instructions, or more formal writing.

A simple way to remember it:

• hay = common in choice questions
• hoặc = more like statement/list or

This is a very natural collocation difference.

1. bằng thang máy

bằng introduces the means/method:

• bằng xe buýt = by bus
• bằng máy bay = by plane
• bằng thang máy = by elevator

2. đi cầu thang

With stairs, Vietnamese usually says đi cầu thang or đi thang bộ, not bằng cầu thang in this kind of sentence.

So the language treats them a little differently:

• elevator = a means you use
• stairs = an action/path you take on foot

Also, in everyday Vietnamese, people very often say:

• đi thang máy
• đi cầu thang

So this sentence is natural, but it is not the only possible phrasing.

Yes. It applies to both choices.

Vietnamese often leaves out repeated words when the meaning is already clear. So:

• bạn đến bằng thang máy hay đi cầu thang?

is understood as something like:

• bạn đến bằng thang máy hay (bạn) đi cầu thang?

The second half is shortened because repeating everything would sound heavy or unnecessary.

English does this too sometimes:

• Are you coming by elevator or taking the stairs?

You do not have to repeat every element if the structure is clear.

Often, yes.

If the speaker is on a higher floor and asking how someone will come up, many speakers would naturally say:

• Bạn lên bằng thang máy hay đi cầu thang?

Why?

• đến focuses on arriving/coming
• lên focuses on going up

Since the sentence mentions a floor in a building, lên can match the situation more directly.
That said, đến is still understandable, especially if the focus is on the person coming to where you are.

Yes, they are natural enough, especially for learners and neutral textbook Vietnamese.

• tôi = a fairly neutral/polite way to say I
• bạn = you, often used for a friend, peer, or neutral conversational partner

However, in real life, Vietnamese often uses relationship words, age-based terms, or names instead of a fixed word for you. So native speech may use things like:

• anh
• chị
• em
• cô
• chú
• a person’s name

So tôi / bạn is correct and useful, but not the only way people would speak in everyday life.

Breaking them apart can help memory:

• thang máy

  • thang = ladder / stair structure
  • máy = machine
    So thang máy is literally something like machine stair/ladder, meaning elevator.

• cầu thang

  • cầu here is part of the compound meaning staircase structure
  • thang relates to ladder/stairs
    Together, cầu thang means stairs / staircase.

You may also hear:

• thang bộ = stairs used on foot

Yes. Very often.

Some natural shorter versions are:

• Tôi ở tầng một. Bạn đi thang máy hay cầu thang?
• Tôi đang ở tầng một. Bạn lên thang máy hay đi cầu thang?
• Tôi ở tầng một; bạn đi thang máy hay đi cầu thang?

Vietnamese often drops words that are predictable from context. Once it is clear you are asking about the person’s way of coming up, the sentence can be made more compact.

Not especially. It is mostly a punctuation choice.

The semicolon links two closely related ideas:

• Tôi đang ở tầng một
• bạn đến bằng thang máy hay đi cầu thang?

You could also write this as:

• two separate sentences
• one sentence with a comma in informal writing
• one sentence with a connector, depending on style

So the semicolon is not a special grammar feature of Vietnamese here. It just shows a pause between two connected parts.