Jak tylko wrócimy z podróży, zmienię prześcieradło i położę nową kołdrę na łóżku.

Jak tylko is a fixed expression meaning as soon as.

So:

• Jak tylko wrócimy z podróży... = As soon as we return from the trip...

Literally, the individual words might not help much, because this is an idiomatic phrase. It is very common in Polish for introducing the first action that triggers the next one.

That is a very common English-speaker question.

In Polish, after jak tylko, it is normal to use a future form if the meaning is future:

• Jak tylko wrócimy...
• Jak tylko przyjdziesz...
• Jak tylko skończą...

So Polish does not follow the same tense pattern as English here.

Also, wrócimy is from the perfective verb wrócić, so it means a completed future event: we will come back / once we have come back.

Because wrócimy means we will return, while wrócę means I will return.

The sentence uses two different subjects:

• wrócimy = we will return
• zmienię = I will change
• położę = I will put/place

So the meaning is something like:

• As soon as we return from the trip, I will change the sheet and put a new duvet on the bed.

The first action is done by we, but the next two actions are done by I.

Because Polish often leaves subject pronouns out when they are already clear from the verb ending.

Here the endings tell you who is doing the action:

• wrócimy = we
• zmienię = I
• położę = I

So adding my or ja is usually unnecessary unless you want special emphasis or contrast.

For example:

• Jak tylko wrócimy z podróży, ja zmienię prześcieradło...

This would sound more emphatic, as if stressing that I will do it.

Here z means from, and in that meaning it requires the genitive case.

So:

• podróż = nominative
• z podróży = genitive after z meaning from

This is different from another use of z, which can mean with and then takes the instrumental:

• z kolegą = with a friend

So this is an important distinction:

• z podróży = from the trip
• z kimś = with someone

Because these are perfective verbs:

• zmienić → zmienię
• położyć → położę

Perfective verbs in Polish form the future with a simple one-word form. They usually express a completed, one-time action.

So:

• zmienię prześcieradło = I’ll change the sheet
• położę nową kołdrę = I’ll put down a new duvet

If you used an imperfective future such as będę zmieniać or będę kłaść, it would suggest a more ongoing, repeated, or process-like action, which is not the most natural choice here.

Because both are direct objects, so they are in the accusative case, but they belong to different genders and declension patterns.

1. prześcieradło

This is a neuter noun.
In the singular, neuter nouns often have the same form in nominative and accusative.

• nominative: prześcieradło
• accusative: prześcieradło

So after zmienię, it stays the same.

2. nową kołdrę

This is a feminine noun phrase, so both the adjective and the noun change in the accusative singular:

• nominative: nowa kołdra
• accusative: nową kołdrę

That is why you see both endings change.

Excellent question. Your instinct is right.

With na, Polish usually distinguishes:

• na łóżku = on the bed → location → locative
• na łóżko = onto the bed → destination → accusative

Because położyć means to put/place, standard Polish would usually prefer:

• położę nową kołdrę na łóżko

If the intended meaning is I will put a new duvet onto the bed, na łóżko is the more standard and expected form.

So na łóżku in this sentence may sound less standard to many speakers, because it looks like a location phrase rather than a destination phrase.

Because Jak tylko wrócimy z podróży is a subordinate clause, and in Polish subordinate clauses are normally separated by a comma from the main clause.

So the structure is:

• Jak tylko wrócimy z podróży, = subordinate clause
• zmienię prześcieradło i położę nową kołdrę na łóżku. = main clause

This comma is standard Polish punctuation.

Yes. Polish word order is fairly flexible, because the endings carry a lot of the grammatical information.

The given sentence is natural, but other orders are possible for emphasis, for example:

• Jak tylko wrócimy z podróży, położę nową kołdrę na łóżko i zmienię prześcieradło.
• Zmienię prześcieradło i położę nową kołdrę na łóżko, jak tylko wrócimy z podróży.

The meaning stays broadly the same, but the emphasis changes slightly. The original order is straightforward and neutral.