Lütfen sakin konuş.

• Lütfen = please
• sakin = calm, calmly, or sometimes quiet/calm in manner depending on context
• konuş = speak! / talk!

So the sentence is literally something like Please, speak calmly.

Turkish often leaves out subject pronouns when they are already clear from the verb form.

In konuş, the form shows that the speaker is addressing you in the singular informal sense, so sen is not needed.

You could say Sen lütfen sakin konuş, but that usually sounds unnecessary unless you want emphasis.

Konuş is the imperative form of the verb konuşmak (to speak / to talk) for second person singular.

So:

• konuşmak = to speak
• konuş = speak!

This is the form used when telling one person to do something.

Konuşmak is the dictionary form, like to speak in English.

When giving a command in Turkish, you usually use the imperative stem:

• konuşmak = to speak
• konuş = speak!

So Lütfen sakin konuş means Please speak calmly, not Please to speak calmly.

It is originally an adjective meaning calm, but in sentences like this it works adverbially in English terms: calmly.

Turkish often uses words like this without adding a special -ly ending the way English does.

So:

• sakin biri = a calm person
• sakin konuş = speak calmly

Its core meaning is speak calmly.

Depending on the situation, English might translate it more naturally as:

• Please calm down when you speak
• Please speak in a calm tone
• sometimes Please speak more quietly if the issue is emotional intensity

But it does not directly mean speak slowly. For that, Turkish would more naturally use yavaş konuş.

So:

• sakin konuş = speak calmly
• yavaş konuş = speak slowly
• sessiz konuş or kısık sesle konuş = speak quietly / in a low voice

Yes, adding lütfen makes it polite.

However, konuş is still an imperative, so the tone depends on context and voice. It can sound:

• friendly and normal
• firm
• slightly direct if said sharply

So Lütfen sakin konuş is polite, but still fairly direct: Please speak calmly.

Yes. Konuş is for one person, usually informal singular.

For a more polite or plural form, use konuşun:

• Lütfen sakin konuşun. = Please speak calmly.
  This can mean:
  • speaking to one person politely
  • speaking to more than one person

So:

• konuş = speak! (singular informal)
• konuşun = speak! (plural or polite singular)

Yes. Lütfen is flexible.

All of these are possible:

• Lütfen sakin konuş.
• Sakin konuş lütfen.
• Sakin lütfen konuş.

The first one is the most neutral and common.

Placing lütfen at the end can sometimes sound a little more conversational:

• Sakin konuş, lütfen.

A rough guide for an English speaker:

• Lütfen ≈ LEWT-fen
• sakin ≈ sah-KEEN
• konuş ≈ ko-NOOSH

A few details:

• ü is not the same as English u. It is like the German ü or the French u.
• ş is pronounced sh.
• Stress is often heard as:
  • lütfen
  • sakin
  • konuş

Not always. It is natural, but Turkish speakers may choose different versions depending on tone.

Common alternatives:

• Lütfen sakin olun. = Please be calm.
• Biraz sakin konuş. = Speak a little more calmly.
• Sakin bir şekilde konuş. = Speak in a calm way.
• Lütfen bağırmadan konuş. = Please speak without shouting.

So Lütfen sakin konuş is correct and natural, but it is just one of several ways to express the idea.