Na trybunie powinno się siedzieć spokojnie, kiedy słychać gwizdek sędziego.

Na trybunie means in the stands / on the spectator stand.

Here trybunie is in the locative case, because it follows na in a location meaning.

• na trybunie = on/in the stand(s) as a place
• compare movement:
  • na trybunę = onto the stand(s)

Polish often uses na with places that English might express with in.

This is mostly a matter of normal Polish usage.

With trybuna meaning stand / grandstand / bleachers, Polish usually says na trybunie, not w trybunie, because the stand is thought of as a seating area or platform-like place.

A few similar patterns:

• na stadionie = at the stadium
• na boisku = on the field
• na trybunie = in/on the stands

Even if English uses in, Polish may prefer na.

Powinno się is an impersonal way to say one should, people should, or it is advisable to.

It does not point to one specific person. Instead, it expresses a general rule or expectation.

So:

• Powinno się siedzieć spokojnie = One should sit quietly / People should sit quietly

This is a very common Polish pattern:

• powinno się robić = one should do
• nie powinno się krzyczeć = one should not shout

Because the sentence is impersonal.

• powinien / powinna / powinno normally agree with a specific subject:
  • On powinien siedzieć = He should sit
  • Ona powinna siedzieć = She should sit

But in powinno się siedzieć, there is no named subject. The construction verb + się makes it general and impersonal, like one should.

In this structure, Polish uses the neuter singular form:

• powinno się
• mówi się
• robi się
• nie pali się

Because powinno się works like a modal expression and is followed by an infinitive, much like English should sit.

So the structure is:

• powinno się + infinitive

Examples:

• Powinno się czekać = One should wait
• Powinno się słuchać = One should listen
• Powinno się siedzieć spokojnie = One should sit quietly

Here się helps create the impersonal meaning.

It does not mean oneself here in the literal reflexive sense. Instead, it is part of a very common Polish structure used for general statements.

Compare:

• Myje się = People wash / One washes
• Tu nie pali się = One does not smoke here / Smoking is not allowed here
• Powinno się siedzieć spokojnie = One should sit quietly

So in this sentence, się is grammatical, not really translatable word-for-word.

Because spokojnie is an adverb, and it describes how someone should sit.

• siedzieć spokojnie = sit calmly / sit quietly

If you used spokojny/spokojna, that would be an adjective describing a noun or a person:

• spokojny kibic = a calm fan
• być spokojnym = to be calm

But after a verb like siedzieć, when you want to describe the manner of the action, Polish normally uses an adverb:

• mówić cicho = speak quietly
• iść powoli = walk slowly
• siedzieć spokojnie = sit quietly/calmly

Słychać means it can be heard, one hears, or simply you can hear.

It is another impersonal form. There is no explicit subject like someone hears.

So:

• kiedy słychać gwizdek sędziego = when the referee’s whistle can be heard

This is very common in Polish:

• Słychać muzykę = You can hear music
• Nic nie słychać = Nothing can be heard
• Było słychać krzyki = Shouts could be heard

Because the two nouns have different roles.

• gwizdek is the thing being heard, so it is the direct object
• sędziego means of the referee, so it is in the genitive to show possession

So:

• gwizdek = whistle
• gwizdek sędziego = the referee’s whistle / whistle of the referee

This is a normal Polish possession pattern:

• samochód nauczyciela = the teacher’s car
• głos dziecka = the child’s voice
• gwizdek sędziego = the referee’s whistle

Literally, gwizdek is a whistle as an object. But in context, Polish often uses it to refer to the sound of the whistle.

So here, the sentence most naturally means hearing the referee’s whistle signal.

If someone wanted to focus more clearly on the sound itself, they might also say something like:

• kiedy słychać gwizd sędziego

But gwizdek sędziego is still understandable and natural in context.

Yes. In this sentence, kiedy and gdy are both possible.

• kiedy słychać gwizdek sędziego
• gdy słychać gwizdek sędziego

Both mean when here.

Very roughly:

• kiedy is often a bit more common and neutral
• gdy can sound slightly more formal or literary in some contexts

But in a sentence like this, both are fine.

The basic meaning stays the same even if the word order changes a bit, because Polish word order is fairly flexible.

Original:

• Na trybunie powinno się siedzieć spokojnie, kiedy słychać gwizdek sędziego.

Possible variations:

• Kiedy słychać gwizdek sędziego, na trybunie powinno się siedzieć spokojnie.
• Powinno się siedzieć spokojnie na trybunie, kiedy słychać gwizdek sędziego.

However, the original sounds natural and balanced. Moving words around can slightly change emphasis.

For example, starting with Kiedy słychać... puts more focus on the time condition.

Yes, but the tone changes a little.

• powinno się siedzieć spokojnie = one should sit quietly
• trzeba siedzieć spokojnie = one has to / must sit quietly

So:

• powinno się sounds more like a rule, recommendation, or expected behavior
• trzeba sounds a bit stronger, more necessary or obligatory

In many situations both are possible, but powinno się feels slightly softer and more normative.

It can suggest both, depending on context.

Literally:

• siedzieć = to sit / to be sitting
• spokojnie = calmly / quietly

So the phrase can imply:

• sit quietly
• stay seated calmly
• remain quiet in your seat

Because the sentence is about behavior in the stands when the referee’s whistle is heard, it sounds like a rule about staying calm and not causing disturbance.

It is understandable and fairly natural, especially as a rule or instruction, but it sounds a bit formal or official.

That is mostly because of the impersonal style:

• powinno się
• słychać

A more direct everyday version might be something like:

• Na trybunie należy siedzieć spokojnie, kiedy słychać gwizdek sędziego.
• Na trybunie trzeba siedzieć spokojnie, kiedy słychać gwizdek sędziego.

But the original is completely valid and good Polish.