Czekam przy kasie, a kasjerka pyta, czy płacę kartą.

Czekam is the 1st person singular present tense form of czekać (to wait).

So:

• czekam = I wait / I am waiting
• czekasz = you wait
• czeka = he/she/it waits

In this sentence, the speaker is talking about their own action, so czekam is the correct form.

Because the preposition przy requires the locative case.

• dictionary form: kasa
• locative singular: kasie

So:

• przy kasie = at the checkout / by the cash register

This is a very common pattern in Polish:

• przy stole = at the table
• przy oknie = by the window
• przy kasie = at the checkout

In this sentence, kasa means the checkout, cash register, or till in a shop.

Depending on context, kasa can also mean:

• cash register
• checkout desk
• sometimes even money / cash in informal use

But in przy kasie, the meaning is clearly the place in the shop where you pay.

Kasjerka means female cashier.

Polish often marks gender in job titles:

• kasjer = male cashier
• kasjerka = female cashier

Since the sentence specifically uses the feminine noun, we know the cashier is a woman.

The verb matches that subject:

• kasjerka pyta = the female cashier asks

Here a is a coordinating conjunction. It often translates as and, but it has a slightly different feel from i.

In this sentence:

• Czekam przy kasie, a kasjerka pyta...

it suggests something like:

• I’m waiting at the checkout, and meanwhile the cashier asks...
• I’m waiting at the checkout, and then the cashier asks...

Very often:

• i simply joins things
• a links two things with a mild contrast or change of focus

So a is natural here because the sentence shifts from what I’m doing to what the cashier does.

Pytać is the infinitive, meaning to ask.

Pyta is the 3rd person singular present tense form:

• pytam = I ask
• pytasz = you ask
• pyta = he/she asks

Since the subject is kasjerka (the cashier), we need pyta:

• kasjerka pyta = the cashier asks

Here czy introduces an indirect yes/no question. It means whether or if.

So:

• kasjerka pyta, czy płacę kartą = the cashier asks whether I’m paying by card = the cashier asks if I’m paying by card

This is different from czy used at the beginning of a direct yes/no question, for example:

• Czy płaci pan kartą? = Are you paying by card?

In your sentence, it is embedded inside a bigger sentence, so it becomes an indirect question.

Because this is reported speech from the speaker’s point of view.

The cashier is asking about my payment, so in indirect speech Polish uses the form that matches me:

• czy płacę kartą = whether I’m paying by card

So even though kasjerka is the subject of pyta, the verb płacę refers to the speaker:

• I wait
• the cashier asks
• whether I am paying by card

This is completely normal in Polish.

Because płacić often takes the instrumental case when you say what you pay with.

• dictionary form: karta
• instrumental singular: kartą

So:

• płacę kartą = I pay by card / with a card

This is the same pattern as:

• piszę długopisem = I write with a pen
• jadę autobusem = I go by bus
• płacę gotówką = I pay in cash

Both are good ways to understand it.

In natural English, you would usually say:

• I’m paying by card
• I pay by card

But grammatically, Polish is using the instrumental in a way that is close to with a card.

So kartą is best understood as the means or instrument used for paying.

It can be, but it can also be an example of the narrative present.

Polish, like English, often uses the present tense to make a situation sound vivid:

• Czekam przy kasie, a kasjerka pyta...
• literally: I’m waiting at the checkout, and the cashier asks...

This can describe:

1. something happening right now, or
2. a past event told as if it is unfolding now

English does this too:

• So I’m standing there, and this woman asks me...

So the present tense here is very natural.

Yes, you could, but it would sound a little different.

• Czekam przy kasie i kasjerka pyta...
  This is understandable, but less natural.

• Czekam przy kasie, a kasjerka pyta...
  This sounds smoother and more idiomatic.

Why? Because a often works well when one clause sets the scene and the next clause moves to another subject or action.

So a is the better choice here.

Yes. Polish word order is flexible, though some versions sound more natural than others.

For example:

• Kasjerka pyta, czy płacę kartą, a ja czekam przy kasie.
• Przy kasie czekam, a kasjerka pyta, czy płacę kartą.

These are grammatical, but the original:

• Czekam przy kasie, a kasjerka pyta, czy płacę kartą.

sounds the most neutral and natural if you want to tell the story in that order.

Because przy kasie and na kasie usually mean different things.

• przy kasie = at the checkout / by the register
• na kasie often means working on the till / at the register as staff

So if you are a customer standing there, przy kasie is the normal phrase.

If someone says:

• Ona pracuje na kasie that usually means:
• She works on the checkout / as a cashier

Yes, płacę comes from płacić, which is imperfective.

That makes sense here because the cashier is asking about the method of payment, not emphasizing a completed one-time result.

• płacić kartą = to pay by card
• zapłacić is the perfective partner and means more like to pay, to make the payment completely

In a question at the checkout, Polish usually prefers the imperfective idea:

• Płaci pan kartą?
• Płaci pani gotówką?

This is the normal everyday wording.

A direct version would usually be something like:

• Płaci pan kartą? — if speaking to a man
• Płaci pani kartą? — if speaking to a woman
• less formally: Płacisz kartą?

Your sentence gives that idea indirectly:

• kasjerka pyta, czy płacę kartą = the cashier asks if I’m paying by card

So the grammar changes because it is reported speech, but the meaning comes from that kind of direct question.

They are not interchangeable.

• czy introduces a yes/no question
• że introduces a statement

So:

• pyta, czy płacę kartą = asks whether I’m paying by card
• mówi, że płacę kartą = says that I’m paying by card

Use czy when the content is uncertain and being asked about. Use że when the content is being stated.

A few useful points:

• cz in czekam sounds roughly like ch in check
• sz in kasjerka sounds like sh
• pyta starts with a hard Polish p, and y is not like English ee
• ę in płacę and kartą is a nasal vowel, though in normal speech its exact pronunciation can vary depending on position

A rough learner-friendly pronunciation guide might be:

• Czekam ≈ CHE-kam
• przy ≈ pshi or pzhi depending on your approximation
• kasie ≈ KA-shye
• kasjerka ≈ ka-SYER-ka
• pyta ≈ PIH-ta
• płacę ≈ PWA-tseh
• kartą ≈ KAR-taw̃

Not perfect, but enough to help you start recognizing the sounds.

Yes. It sounds natural and idiomatic.

It uses very common Polish patterns:

• czekać przy kasie
• kasjerka pyta
• czy...
• płacić kartą

So this is exactly the kind of sentence you might hear or say in an everyday shopping situation.