Proszę mówić krótko i jasno.

Yes — proszę has several common uses in Polish, and this is one of them.

In Proszę mówić krótko i jasno, proszę is a polite way to say please before a verb. It softens the command and makes it sound courteous.

Common meanings of proszę include:

• please → Proszę usiąść. = Please sit down.
• here you are → Proszę, kawa. = Here’s your coffee.
• go ahead / what can I do for you?
• you’re welcome in some situations

So in this sentence, proszę is functioning as a polite marker: Please speak...

After proszę, Polish very often uses the infinitive to make a polite request or instruction.

So:

• Proszę mówić = Please speak
• Proszę poczekać = Please wait
• Proszę usiąść = Please sit down

This is one of the most common polite patterns in Polish.

Compare:

• Mów krótko i jasno. = Speak briefly and clearly.
  This is more direct, less polite.
• Proszę mówić krótko i jasno. = Please speak briefly and clearly.
  This is polite.

So the infinitive is not random — it is part of the structure proszę + infinitive.

This is mainly about aspect and the kind of action being requested.

• mówić = imperfective, focusing on the process or manner of speaking
• powiedzieć = perfective, focusing more on saying something as a complete act

In Proszę mówić krótko i jasno, the speaker is asking about how someone should speak: briefly and clearly. That suits mówić very well.

If you said:

• Proszę powiedzieć krótko i jasno

it would sound more like Please say it briefly and clearly or state it briefly and clearly, focusing more on delivering one complete statement.

Both can exist in context, but mówić is the more natural choice for a general instruction about manner of speaking.

They are adverbs.

They describe how someone should speak:

• krótko = briefly / shortly
• jasno = clearly

They come from adjectives:

• krótki = short
• jasny = clear / bright

Polish often forms adverbs from adjectives in this way:

• szybki → szybko = quickly
• głośny → głośno = loudly
• dokładny → dokładnie = accurately

Since they describe the verb mówić, adverbs are needed here, not adjectives.

Because the sentence needs an adverb, not an adjective.

• krótki / krótka / krótkie are adjective forms meaning short
• krótko is the adverb meaning briefly / shortly

You use an adjective to describe a noun:

• krótka odpowiedź = a short answer

You use an adverb to describe a verb:

• mówić krótko = to speak briefly

The same is true for jasno:

• jasna odpowiedź = a clear answer
• mówić jasno = to speak clearly

i simply means and.

So:

• krótko i jasno = briefly and clearly

It joins two adverbs describing the same verb mówić.

This is very straightforward and works like English:

• Speak briefly and clearly
• Mów krótko i jasno

It is polite and neutral, and it can be used in both formal and semi-formal situations.

Because it uses proszę + infinitive, it sounds courteous. It is often heard in:

• offices
• customer service
• classrooms
• official instructions
• polite conversation

It is less personal than using pan/pani directly, but still polite.

Compare:

• Mów krótko i jasno. = direct, informal, possibly blunt
• Proszę mówić krótko i jasno. = polite request/instruction
• Proszę mówić krótko i jasno, panie Tomaszu. = explicitly polite and directed to one person

By itself, Proszę mówić krótko i jasno does not explicitly show number the way an imperative like mów or mówcie would.

It can be used:

• to one person
• to a group
• as a general instruction

That is one reason this structure is useful: it is polite and somewhat impersonal.

Context tells you who is being addressed.

For comparison:

• Mów krótko i jasno. = singular informal
• Mówcie krótko i jasno. = plural informal
• Proszę mówić krótko i jasno. = polite instruction; number is not the main point

Yes. That would also be correct.

• krótko i jasno = briefly and clearly
• zwięźle i jasno = concisely and clearly

The version with krótko is very common and natural in everyday Polish.
zwięźle sounds a bit more formal or sophisticated.

So the sentence in your example is natural, idiomatic, and easy to understand.

The normal stress pattern in Polish is on the second-to-last syllable of each word:

• PRO-szę
• MÓ-wić
• KRÓT-ko
• JAS-no

A few pronunciation notes:

• sz sounds like English sh
• ó is pronounced like u
• ć is a soft ch-like sound, similar to a very soft tch
• j is like English y in yes

So a rough pronunciation guide is:

• Proszę mówić krótko i jasno
  ≈ PRO-sheh MOO-veech KROOT-ko ee YAS-no

This is only approximate, but it helps.

Yes, Polish word order is fairly flexible, but the basic version:

• Proszę mówić krótko i jasno

is the most neutral and natural.

You might change the order for emphasis, for example:

• Proszę mówić jasno i krótko.
• Krótko i jasno, proszę mówić.

These are possible, but the original sentence is the simplest and most standard.

For learners, it is best to remember the neutral pattern:

proszę + infinitive + adverbs/details

It can function as any of those, depending on context, but grammatically it is a polite request/instruction.

Tone matters:

• said gently, it is a request
• said in a meeting or official context, it may sound like an instruction
• said sharply, it can feel like a polite command

So proszę makes it polite, but it does not automatically make it soft in every situation. Context and intonation still matter.