Na koncert kupiliśmy zarówno zwykły bilet, jak i bilet powrotny na nocny pociąg.

In Polish, na + accusative is the normal way to say “for / to (an event)”:

• na koncert – to/for a concert
• na film – to a movie
• na mecz – to a match
• na spotkanie – to a meeting

It can express:

• destination: dokąd? (where to?) → Idziemy na koncert. – We’re going to the concert.
• purpose: po co? (for what?) → Kupiłem bilet na koncert. – I bought a ticket (for) the concert.

dla koncertu would mean “for the benefit of the concert” (as in “for the sake of the concert”), which sounds wrong here.

do koncertu is ungrammatical in this sense; do is used with places (do domu, do pracy, do kina), not events.

Koncert is in the accusative singular after the preposition na.

For masculine inanimate nouns like koncert, the nominative and accusative forms are the same:

• Nominative: koncert (To jest koncert.)
• Accusative: koncert (Idę na koncert.)

So you recognize the case from the context and preposition:

• na + accusative (here: na koncert) = “to/for (an event)”

Zarówno … jak i … is a fixed construction meaning “both … and …”.

In this sentence:

• zarówno zwykły bilet, jak i bilet powrotny
  = both a regular ticket and a return ticket

Usage notes:

• zarówno goes before the first element:
  • Kupiłem zarówno chleb, jak i mleko. – I bought both bread and milk.
• jak i introduces the second element.
• It’s more emphatic / formal than a simple i (“and”).

You can often replace it with “both X and Y” in English.

Yes, grammatically that’s fine:

• Na koncert kupiliśmy zwykły bilet i bilet powrotny na nocny pociąg.

This would simply mean “We bought a regular ticket and a return ticket…”.

The difference:

• i – neutral, just lists two things.
• zarówno … jak i … – highlights that there were two kinds of things, stressing the “both … and …” contrast.

So the original version is a bit more emphatic or stylistically richer.

Kupiliśmy is:

• past tense
• 1st person plural (“we”)
• masculine/mixed-gender group (at least one male present)
• perfective aspect (completed action)

Formally it’s:

• kupi- (verb stem: “buy”)
• -li (past masculine personal ending)
• -śmy (1st person plural clitic = “we”)

So:

• kupiliśmy – we (at least one male) bought
• kupiłyśmy – we (all female) bought

Polish often drops the subject pronoun:

• Kupiliśmy bilety. – We bought tickets.
  (My kupiliśmy bilety is possible but usually not needed.)

You technically can say:

• Na koncert kupiliśmy zarówno zwykły, jak i powrotny bilet.

It would mean the same thing and is grammatically correct.

However:

• Repeating bilet (zwykły bilet, jak i bilet powrotny) makes the contrast clearer and avoids any momentary ambiguity.
• With longer phrases (like bilet powrotny na nocny pociąg), repetition often sounds clearer and more natural.

So the original:

• … zarówno zwykły bilet, jak i bilet powrotny na nocny pociąg
  sounds very natural and unambiguous.

In this context:

• zwykły bilet – literally “a normal / regular ticket”.
  Depending on context, zwykły bilet could mean:

  • a standard (non-discounted) ticket (as opposed to ulgowy – reduced)
  • or a one-way ticket (as opposed to powrotny – return)

• bilet powrotny – a return ticket (a ticket for the way back).

From the whole sentence, a natural interpretation is:

• a regular concert ticket (entry ticket)
• plus a return train ticket for the night train

Nocny here describes pociąg (train), not the ticket:

• bilet powrotny – return ticket
• na nocny pociąg – for the night train

So the structure is:

• [bilet powrotny] [na nocny pociąg]
  = a return ticket for the night train.

If you really wanted to stress a “night return ticket” (ticket valid only at night), you’d normally still phrase it via the train or journey, not the ticket itself: bilet powrotny na nocne połączenie etc.

Again, na + accusative is used for destination / purpose:

• na nocny pociąg – for the night train (with the idea of getting on that train)

Compare:

• bilet na pociąg – a ticket for the train
• bilet do pociągu – sounds odd; do isn’t used for “for a train” in this sense
• w pociągu – in the train (locative)

So na nocny pociąg answers “na co?” (“for what?”) and takes the accusative: pociąg → pociąg.

Polish word order is fairly flexible. Both are possible:

• Na koncert kupiliśmy zarówno zwykły bilet, jak i bilet powrotny…
• Kupiliśmy na koncert zarówno zwykły bilet, jak i bilet powrotny…

The difference is one of emphasis:

• Starting with Na koncert puts “for the concert” in focus or as the topic:
  As for the concert, we bought…
• Starting with Kupiliśmy is more neutral, focusing on the action of buying.

So the chosen order lightly emphasizes the context “for the concert”.

In everyday Polish, the adjective before noun order is by far the most common:

• nocny pociąg – night train
• szybki pociąg – fast train
• międzynarodowy pociąg – international train

You can sometimes see noun + adjective (e.g. in official names, titles, or poetic style), but:

• pociąg nocny would usually sound marked, stylistic, or like the official name of a specific connection rather than a neutral description.

So nocny pociąg is the natural, default wording.