Jeg går ikke ud af supermarkedet, før jeg har betalt ved kassen.

Supermarkedet is the definite form of supermarked:

• et supermarked = a supermarket
• supermarkedet = the supermarket

In Danish, the definite article is usually added to the end of the noun as a suffix:

• en bil → bilen
• et hus → huset
• et supermarked → supermarkedet

So ud af supermarkedet means out of the supermarket.

Går ud af means go out of / leave.

It is made up of:

• går = go / walk
• ud = out
• af = of / out of in this expression

Together, gå ud af works like a fixed expression meaning to go out of a place:

• Jeg går ud af huset = I go out of the house
• Han går ud af bilen = He gets out of the car

So in your sentence, går ud af supermarkedet means leave the supermarket.

In a normal Danish main clause, the finite verb usually comes in second position. After that, ikke often comes later.

So:

• Jeg går ikke ud af supermarkedet

has this basic structure:

• Jeg = subject
• går = finite verb
• ikke = negation

This is very common in Danish main clauses:

• Jeg spiser ikke kød
• Han kommer ikke i dag
• Vi bor ikke her

English says I do not go, but Danish does not need do-support. It simply says Jeg går ikke.

In Danish, før can mean before, but in negative sentences like this it often corresponds to English until.

So:

• Jeg går ikke ud af supermarkedet, før jeg har betalt ved kassen

literally looks like:

• I do not go out of the supermarket, before I have paid at the checkout

but the natural English meaning is:

• I’m not leaving the supermarket until I’ve paid at the checkout

This is a very common pattern:

• Jeg går ikke i seng, før jeg er færdig.
• Han tager ikke hjem, før arbejdet er gjort.

So learners should remember: after a negative main clause, før is often best translated as until.

Jeg har betalt is the present perfect and means I have paid.

It is used because the payment must be completed first before the action in the main clause happens. The speaker will not leave the supermarket until the paying is already done.

• har = have
• betalt = paid

So:

• før jeg har betalt = until I have paid

This emphasizes a finished action.

If you said før jeg betaler, it would sound less natural in this context for many learners’ intended meaning, because the idea is not just until I pay, but until I have paid — the payment must be completed.

After før, you get a subordinate clause. In Danish subordinate clauses, the word order is different from main clauses.

Here the clause is:

• før jeg har betalt ved kassen

The usual order is:

• conjunction
• subject
• sentence adverb / negation
• finite verb
• other elements

But since there is no ikke inside this subordinate clause, you simply get:

• før
  • jeg
    • har
      • betalt

Compare:

• Main clause: Jeg går ikke ud
• Subordinate clause: før jeg ikke går ud would place ikke before the finite verb in the subordinate clause

A useful contrast:

• Jeg kommer ikke.
• ..., fordi jeg ikke kommer.

So the sentence is normal: før jeg har betalt ved kassen.

Ved kassen means at the checkout, at the cash register, or at the till.

• ved = at / by / near
• kassen = the register / checkout

In a supermarket context, kassen usually means the place where you pay.

So:

• betalt ved kassen = paid at the checkout

This is more idiomatic than translating word-for-word as something like by the box, even though kasse can mean box in other contexts.

Just like supermarkedet, kassen is the definite form:

• en kasse = a box / a till / a checkout
• kassen = the box / the till / the checkout

In this context, Danish often uses the definite form because it refers to the checkout area as a known part of the supermarket.

So ved kassen is the normal idiomatic way to say at the checkout.

Yes. Danish often uses the present tense for something that applies now, as a rule, or in a near-future sense.

So:

• Jeg går ikke ud af supermarkedet, før jeg har betalt ved kassen

can mean something like:

• I’m not leaving the supermarket until I’ve paid
• I won’t leave the supermarket until I’ve paid

Danish does not always need a separate future form like English will. The present tense is often enough when the meaning is clear from context.

Yes, you could say:

• Jeg forlader ikke supermarkedet, før jeg har betalt ved kassen.

That means essentially the same thing: I do not leave the supermarket until I have paid at the checkout.

The difference is style:

• går ud af supermarkedet = more everyday, literal, physical go out of
• forlader supermarkedet = more formal or neutral leave

A native speaker would understand both, but går ud af feels very natural in ordinary speech.

Not always. It depends on what follows.

You use ud af when you are going out of something:

• ud af huset = out of the house
• ud af bilen = out of the car
• ud af supermarkedet = out of the supermarket

But if you simply mean go outside, you often just use ud:

• Jeg går ud = I’m going out / outside

So in this sentence, af is needed because the speaker is leaving a specific place: supermarkedet.