Kiedy syrena była już blisko, dzieci przestały płakać i spokojnie zeszły na dół.

Because Kiedy syrena była już blisko is a subordinate clause introduced by kiedy (when). In Polish, subordinate clauses are normally separated from the main clause with a comma.

So the sentence is divided like this:

• Kiedy syrena była już blisko, = When the siren was already close,
• dzieci przestały płakać i spokojnie zeszły na dół. = the children stopped crying and calmly went downstairs.

This comma is required in standard Polish.

Here, kiedy means when.

It introduces a time clause:

• Kiedy syrena była już blisko... = When the siren was already near...

A learner should notice that Polish uses kiedy very much like English when in this kind of sentence.

You can also put the clauses in the opposite order:

• Dzieci przestały płakać i spokojnie zeszły na dół, kiedy syrena była już blisko.

But the version with kiedy first sounds very natural and sets the scene first.

Because syrena is a feminine singular noun, and the past tense in Polish agrees with the subject in gender and number.

The infinitive is być = to be.

Past tense:

• był = he/it was
• była = she/it was
• było = it was
• byli / były = they were

Since syrena is feminine:

• syrena była = the siren was

So była is used simply because of grammatical gender.

Już usually means already.

So:

• była blisko = was close / was near
• była już blisko = was already close

It adds the idea that the siren had reached that point by then. It often gives a sense of progression or change of situation.

In many contexts, już can also sound slightly like:

• by then
• at that point already

Here blisko is functioning like near / close after być.

In Polish, blisko is very often used predicatively:

• Dom jest blisko. = The house is near.
• Syrena była już blisko. = The siren was already close.

English speakers may expect something more like was near with an adjective, but Polish commonly uses blisko in this structure.

You will also see:

• blisko domu = near the house
• bardzo blisko = very close

So the important pattern is:

• być blisko = to be near

It can mean both, depending on context.

Common meanings of syrena:

1. siren (alarm, emergency vehicle sound)
2. mermaid

In this sentence, the context clearly points to siren, because it says:

• the siren was getting close
• the children stopped crying
• they went downstairs

So this is not about a mermaid.

This is a good example of how context decides the meaning.

This is a very common learner question.

Dzieci means children, but grammatically it behaves differently from many other words referring to people. In the past tense, it normally takes the non-masculine-personal plural ending:

• dzieci przyszły
• dzieci bawiły się
• dzieci przestały płakać

So:

• przestały is correct
• przestali would not be used with dzieci

Even though children are people, the noun dzieci follows this special agreement pattern.

Because przestać is followed by an infinitive.

Pattern:

• przestać + infinitive = to stop doing something

Examples:

• przestać płakać = to stop crying
• przestać mówić = to stop talking
• przestać biegać = to stop running

So:

• dzieci przestały płakać = the children stopped crying

This is very similar to English stop + -ing, but in Polish you use the infinitive, not a separate gerund form.

Przestać is a perfective verb, and that fits the meaning here very well.

Perfective verbs in Polish often show a completed event or a clear change:

• przestały płakać = they stopped crying
  (the crying came to an end)

If you used an imperfective verb, the meaning would be different or unnatural here. The sentence wants to express a completed transition: first they were crying, then they were not.

So przestały is exactly the right choice.

Spokojnie is an adverb, meaning calmly or quietly.

It describes how they went downstairs:

• spokojnie zeszły = they went down calmly

Compare:

• spokojny / spokojna / spokojne / spokojni = adjective forms meaning calm
• spokojnie = adverb meaning calmly

So:

• spokojne dzieci = calm children
• dzieci spokojnie zeszły na dół = the children calmly went downstairs

Zeszły na dół specifically means went down or went downstairs.

The verb is zejść (perfective), from schodzić / zejść:

• schodzić = to be going down / to go down repeatedly
• zejść = to go down, to descend, to come down (completed action)

So:

• zeszły na dół = they went downstairs / they went down

If you said:

• poszły na dół

that can also mean they went downstairs, and it is possible in many contexts. But zeszły na dół emphasizes the downward movement more directly.

So the version in the sentence is a bit more vivid and literal: they actually descended.

Because na dół is the normal idiomatic expression for downstairs / down / to the lower floor.

Examples:

• Idę na dół. = I’m going downstairs.
• Zeszli na dół. = They went downstairs.

Even though English speakers may expect something like to the bottom, Polish uses na dół very naturally in this situation.

Do dołu would usually not be used for go downstairs in this everyday sense.

For the same reason as przestały: the subject is dzieci.

Since dzieci takes non-masculine-personal plural agreement, the past tense uses -ły:

• dzieci przestały
• dzieci zeszły

This agreement is consistent across the coordinated verbs in the sentence.

Yes, but it is mostly about style and emphasis, not basic grammar.

The order is very natural:

• dzieci = subject
• przestały płakać = first action
• i spokojnie zeszły na dół = second action

This creates a clear sequence:

1. they stopped crying
2. they calmly went downstairs

The adverb spokojnie comes before zeszły, which is a normal place for it.

You could rearrange parts of the sentence for emphasis, for example:

• Dzieci spokojnie zeszły na dół i przestały płakać.

But that changes the flow and may slightly suggest a different sequence. The original sentence is clearer because it presents the actions in the likely order they happened.

Zeszły comes from zejść, which is perfective.

That means the action is presented as completed:

• they went downstairs
• the movement was finished

This matches the structure of the whole sentence, which describes completed events:

• syrena była już blisko
• dzieci przestały płakać
• zeszły na dół

If you used the imperfective schodziły, it would suggest ongoing or repeated action:

• dzieci schodziły na dół = the children were going downstairs / used to go downstairs

But here the sentence describes one completed event, so zeszły is the right form.