I need a mentor on Bitcoin earnings. Some one who can teach me how to earn from bitcoins
You need a mentor only if you are lazy. And then you will only get scammed.
Learn by doing. Read a lot. If you cannot find some info, ask, but be prepared for nice and not nice answers, especially for things that you could have googled first.
Some said about exchanges - play with them, but on small amounts, only to get the idea.
Be careful and extra careful. Scams pop out on daily basis and not all answers are what you'd think: some want to help you, some want to deceive you and help themselves.
However, the only good way to learn is to try. This way you'll know what to ask here.