Przestań proszę mówić tak głośno.

Przestań means stop.

It is the imperative form of the verb przestać, which means to stop or to cease.
More specifically, przestań is the command form used when speaking to one person.

Related forms:

• przestań = stop! (to one person)
• przestańcie = stop! (to more than one person)

So the sentence is directed at one listener.

Because in Polish, after przestać you normally use an infinitive to say stop doing something.

So:

• przestań mówić = stop talking
• przestań krzyczeć = stop shouting
• przestań płakać = stop crying

This works very similarly to English stop + -ing, but Polish uses the infinitive instead.

Here proszę means please.

It softens the command a little, so Przestań proszę mówić tak głośno is less abrupt than just Przestań mówić tak głośno.

However, it is still a command, not a neutral question. So it may still sound fairly firm, depending on tone.

Also, proszę can mean other things in other contexts, such as:

• please
• here you are
• go ahead
• I’m asking

But in this sentence, it is simply please.

It is firm, but not automatically rude.

Without proszę, it sounds more direct:

• Przestań mówić tak głośno. = Stop talking so loudly.

With proszę, it becomes softer:

• Przestań proszę mówić tak głośno. = Please stop talking so loudly.

Still, because it is an imperative, it can sound:

• normal in a practical situation
• parental or teacher-like
• annoyed, if said sharply

If you want something softer and more indirect, Polish often uses a question instead:

• Czy możesz mówić ciszej? = Can you speak more quietly?
• Mógłbyś mówić trochę ciszej? = Could you speak a bit more quietly?

Because głośno is an adverb, and it describes how someone is speaking.

• głośny / głośna / głośne = loud (adjective)
• głośno = loudly / loud (adverb)

In this sentence, the word describes the verb mówić:

• mówić głośno = to speak loudly

Compare:

• To jest głośny człowiek. = He is a loud person.
• On mówi głośno. = He speaks loudly.

Here tak means so.

So:

• tak głośno = so loudly / so loud

It expresses degree, just like English so in so loud.

Compare:

• tak głośno = so loudly
• bardzo głośno = very loudly

The difference is small but useful:

• bardzo głośno sounds more like a general description: very loudly
• tak głośno often reacts to the current situation: this loud / so loud

Because Polish often omits subject pronouns when the verb form already shows the person.

Here, przestań already tells you that the speaker is talking to you singular.

So:

• Przestań already means you stop
• you do not need ty

If you add ty, it usually gives extra emphasis:

• Ty przestań mówić tak głośno.

That can sound:

• more emotional
• more contrastive
• sometimes more irritated

Normally, leaving ty out is the most natural choice.

Yes, Polish word order is fairly flexible.

These are all possible:

• Przestań proszę mówić tak głośno.
• Proszę, przestań mówić tak głośno.
• Przestań mówić tak głośno, proszę.

The basic meaning stays the same, but the tone changes slightly:

• Proszę at the beginning can sound a little more polite or careful
• proszę in the middle sounds conversational
• proszę at the end can sound like an added softener

The phrase tak głośno usually stays together, because it works as one unit meaning so loudly.

Because mówić refers to the ongoing activity of speaking or talking.

• mówić = to speak / to be talking
• powiedzieć = to say / to tell, usually as a completed act

In this sentence, the speaker wants someone to stop the ongoing action of talking loudly, so mówić is the natural choice.

So:

• Przestań mówić = Stop talking

Using powiedzieć here would not sound natural in the same way, because powiedzieć focuses more on saying something as a complete utterance.

This is about aspect, which is very important in Polish verbs.

• przestać = perfective
• przestawać = imperfective

In commands like stop now, Polish normally uses the perfective verb:

• Przestań! = Stop!

That is because the speaker wants a clear result: the action should end.

The imperfective imperative przestawaj is much less common and usually does not fit this normal everyday command. For most learners, the natural form to remember is simply:

• przestań + infinitive

A rough English-friendly pronunciation would be:

PSHEH-stań PRO-sheh MOO-vich tak GWO-shno

A few important details:

• rz in przestań sounds like a hard zh/sh sound
• ń is a soft n
• ó sounds like u
• wić in mówić sounds roughly like veech
• gł in głośno sounds like gw
• ś is a soft sound, somewhat like a softened sh

A more IPA-style version is:

/ˈpʂɛstaɲ ˈprɔʂɛ ˈmuvit͡ɕ tak ˈɡwɔɕnɔ/

They are similar, but not exactly the same.

• Przestań mówić tak głośno = Stop talking so loudly.
• Nie mów tak głośno = Don’t talk so loudly.

The first suggests the person is already doing it, and you want them to stop.
The second can mean either:

• stop doing that, or
• don’t do that

So przestań is often stronger and more immediate in this kind of situation.

Yes. In fact, that is the most natural English translation.

A word-for-word breakdown would be:

• Przestań = stop
• proszę = please
• mówić = to speak / to talk
• tak głośno = so loudly

But natural English would usually be:

• Please stop talking so loudly.
• Please stop speaking so loudly.

Both are fine, though talking is a little more everyday in English.