"Nein" means "no". It's the answer to a question. "Nicht" means "not". It's used whenever you want to write a negative sentence. "Bitte" is the same as please. It's used whenever you ask something of someone else, to be polite. So you can translate the examples literally into English, with the same usage: No, please. Please don't. (= do not, English needs a verb here). No, not me.