W sobotę czyszczę akwarium, zanim dzieci wrócą z parku.

Because after w when talking about on a particular day, Polish uses the accusative case.

• sobota = nominative
• sobotę = accusative

So:

• w sobotę = on Saturday
• w niedzielę = on Sunday

This is a very common pattern with days of the week when you mean on that day.

Polish often leaves out subject pronouns because the verb ending already shows who is doing the action.

• czyszczę = I clean / I am cleaning

The ending -ę tells you it is 1st person singular: I.

So ja czyszczę is possible, but usually unnecessary unless you want emphasis, for example:

• Ja czyszczę akwarium, nie ty. = I’m cleaning the aquarium, not you.

In Polish, the present tense of an imperfective verb can be used for:

• a habitual action: I clean the aquarium on Saturdays
• a planned future action: I’m cleaning the aquarium on Saturday

So W sobotę czyszczę akwarium can mean either a routine or a planned action, depending on context.

This is similar to English sentences like:

• On Saturday I’m cleaning the aquarium
• On Saturdays I clean the aquarium

Polish often lets context do the work.

Akwarium is the direct object of czyszczę, so it is in the accusative case. However, for many neuter inanimate nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: akwarium
• accusative: akwarium

That is why the form does not change.

Zanim means before in the sense of before something happens.

In this sentence:

• zanim dzieci wrócą z parku = before the children come back from the park

It introduces a subordinate clause, just like English before.

Compare:

• Zjem obiad, zanim wyjdę. = I’ll eat lunch before I leave.
• Zanim zadzwonisz, napisz wiadomość. = Before you call, send a message.

Because zanim introduces a subordinate clause, and in Polish such clauses are normally separated by a comma.

So:

• W sobotę czyszczę akwarium, zanim dzieci wrócą z parku.

This is standard Polish punctuation.

English is sometimes less strict with commas in similar sentences, but Polish usually requires them.

This is about aspect.

• wracać = imperfective = to be returning / to return repeatedly
• wrócić = perfective = to return, to come back once, to complete the return

The form wrócą comes from the perfective verb wrócić. Perfective verbs do not have a true present meaning in forms like this; their so-called present forms usually refer to the future.

So:

• dzieci wrócą = the children will come back

After zanim, Polish often uses this kind of future-perfective form when talking about a completed future action.

Because in Polish, perfective verbs form the future using forms that look like present-tense endings.

So:

• wrócę = I will return
• wrócisz = you will return
• wrócą = they will return

There is no extra word like English will here.

This is different from imperfective verbs, which usually make the future with będę + infinitive or past-like form, for example:

• będę wracać = I will be returning / I will return
• będą wracać = they will be returning

Dzieci is the plural of dziecko meaning child. It is irregular, so you simply have to learn it as a special plural form.

• singular: dziecko = child
• plural: dzieci = children

In this sentence, dzieci is the subject, so it is in the nominative plural.

The preposition z meaning from requires the genitive case.

• park = nominative
• parku = genitive

So:

• z parku = from the park

This is a very common pattern:

• z domu = from the house
• z miasta = from the city
• z pracy = from work

Be careful: z can also mean with, but then the case is different in some contexts. Here it clearly means from.

Because the two verbs express different kinds of actions.

czyszczę — imperfective

This focuses on the action itself:

• I clean / I am cleaning

It works well for habits, ongoing actions, or planned activities seen as a process.

wrócą — perfective

This focuses on the action being completed:

• the children will come back

After zanim, the idea is that the aquarium cleaning happens before the children have completed their return from the park. So the perfective verb fits naturally.

This contrast is very normal in Polish:

• one action is presented as a process or activity
• the other as a completed event

Yes. W sobotę can sometimes mean on Saturday as a specific upcoming day, but in context it can also sound like part of a routine.

Depending on the situation, the sentence might be understood as:

• On Saturday I’m cleaning the aquarium, before the children come back from the park.
• On Saturdays I clean the aquarium before the children come back from the park.

If you want to make the habitual meaning clearer, Polish often uses:

• W soboty czyszczę akwarium... = On Saturdays I clean the aquarium...

So:

• w sobotę = on Saturday, one Saturday / this Saturday
• w soboty = on Saturdays, regularly

No, Polish word order is fairly flexible, although some orders sound more neutral than others.

The given sentence is natural:

• W sobotę czyszczę akwarium, zanim dzieci wrócą z parku.

But other versions are also possible, for example:

• Czyszczę akwarium w sobotę, zanim dzieci wrócą z parku.
• Zanim dzieci wrócą z parku, w sobotę czyszczę akwarium.

The meaning stays mostly the same, but the focus changes slightly. Polish word order is often used to highlight what is most important or what is already known from context.

Yes, it is a tricky word for English speakers.

czyszczę comes from czyścić and contains several consonant clusters. A rough guide is:

• czy- sounds a bit like chih
• -szcz- is a cluster similar to shch
• -ę at the end is a nasal vowel, often sounding a bit like en/em depending on context

A rough approximation is:

• CHIH-shch-en

But that is only approximate. The important thing is not to pronounce every letter separately in an English way.

Useful related forms:

• czyścić = to clean
• czyszczę = I clean
• czyścisz = you clean
• czyści = he/she/it cleans

This is a verb worth practicing aloud because its spelling and pronunciation are not very transparent for beginners.