You can't overcome shyness. It's best to accept it as it is and move on from there. If you spend your time looking for faults in yourself, you're introverted, ignoring the rest of the people on this planet. It'd be best for you, as it is for everyone else, to get out there and mix with others. Nobody else's perfect, you know. Mixing with them will help you realise you're not so terrible a person after all. Narcissism is far, far more a problem than shyness. And it's not the only one.

Everything starts in your mind and then becomes reality, so you need to put in the right beliefs into your subconscious. This is the most important thing you can do. Try repeating (out loud or in your head) ‘every day in every way I am more and more confident.’ Say it in the shower, on the way to school, in the supermarket, anywhere! You can also try using visualizations – see yourself being outrageously confident in social situations, feel how good that is! Or try self-hypnosis – this is a common technique for embedding new belief systems into your mind.

Do you mean shyness when speaking English or being shy socially?

I don't know, how it is in the place where you are, but in many cities there are centres where psychologists are working with people having difficulties in communication. There are special groups of such shy people, where they are trained to overcome shyness and other difficulties.