Proszę nie mówić naraz.

In this sentence, proszę works like please.

Literally, proszę comes from the verb prosić (to ask/request), so it can also mean I ask or I request. But in everyday Polish, proszę + infinitive is a very common way to make a polite instruction:

• Proszę czekać. = Please wait.
• Proszę usiąść. = Please sit down.
• Proszę nie mówić naraz. = Please don’t all speak at once.

So here it makes the sentence polite, neutral, and natural.

Because this sentence uses the pattern proszę + infinitive.

Polish has more than one way to tell people not to do something:

• Nie mów! = Don’t speak! / Don’t say it!
  
  • singular, informal
• Nie mówcie! = Don’t speak!
  
  • plural, informal
• Proszę nie mówić. = Please don’t speak.
  
  • polite, neutral, often used in public or formal situations

So proszę nie mówić naraz sounds like something a teacher, moderator, receptionist, or announcer might say.

Because after proszę in this kind of polite request, Polish normally uses the infinitive.

So:

• proszę mówić = please speak
• proszę nie mówić = please do not speak

This is a very standard structure in Polish. English learners sometimes expect a conjugated verb after please, but Polish often prefers proszę + infinitive in polite instructions.

Here naraz means at the same time, all at once, or simultaneously.

So the idea is:

• mówić naraz = to speak all at once

That is why the sentence is used when several people start talking together.

A close equivalent would be:

• Proszę nie mówić jednocześnie.

But naraz is very natural in this context.

Grammatically, proszę nie mówić can be used politely to one person or to more than one person, because this structure does not show number clearly.

However, naraz strongly suggests more than one person, because one person cannot really speak all at once by themselves in this sense.

So in real use, the sentence is normally addressed to a group:

• a class
• a meeting
• a family
• an audience

Because in Polish, nie normally goes directly before the verb in negative sentences.

So:

• mówić = to speak
• nie mówić = not to speak

This is completely regular. Also, with verbs, nie is written separately:

• nie mówić
• nie robić
• nie czekać

So nie mówić is correct, not niemówić.

Mówić means to speak / to say / to talk, and it fits well here.

If you said:

• Proszę nie mówić naraz
  you are telling people not to all start speaking at the same time.

You could also hear:

• Proszę nie rozmawiać. = Please don’t talk.
• Proszę nie rozmawiać naraz. = possible, but less typical here
• Proszę nie mówić jednocześnie. = also correct

In this situation, mówić naraz is a very natural choice because the focus is on multiple voices overlapping.

It sounds polite, neutral, and fairly standard.

It is not extremely formal, but it is more polite and controlled than a direct imperative. It works well in situations like:

• a teacher speaking to students
• a host speaking to guests
• a meeting chair speaking to participants
• someone trying to organize a conversation

With friends, people might say something more direct, for example:

• Nie mówcie wszyscy naraz. = Don’t all talk at once.

That version is less formal and more conversational. The version with proszę sounds more courteous.