Learn Turkish: Lütfen konuşma, dinle! - Please do not speak, listen!

To tell someone not to do something, we take the verb root and add the negative suffix -ma or -me. The root of konuşmak (to speak) is konuş-. Since the last vowel in the root is "u", vowel harmony dictates we use -ma, creating konuşma (do not speak!).

Why does "dinle" have no endings at all?

In Turkish, the positive command form for an informal "you" (singular) is just the bare verb root. If you take the dictionary form dinlemek (to listen) and remove the -mek, you are left with dinle, which means "listen!".

Do I need to include the word "sen" (you) in this sentence?

No, it is usually dropped. The command forms of the verbs already tell us exactly who is being spoken to. You could say "Lütfen sen konuşma, sen dinle!", but it sounds unnatural unless you want to put heavy emphasis on who should do the action.

Is it polite to use these short command forms if I say "Lütfen" (please)?

Adding Lütfen makes it softer, but these short forms (konuşma, dinle) are still informal. You should only use them with friends, family, or people younger than you. For strangers or formal situations, Turkish has a more polite command ending that you will learn later.