The best way to improve is to talk to others. Make your mistakes here, and you will be better when you speak to others in your life.

Thanks for all of you that giving me so many advice! I will try my best to learn it !

If you are shy to speak English, that is a natural feeling. Everyone is shy to speak a second language, but no one should be scared. This is a great thing that you are doing. Learning a second language is difficult. Most people understand that it is difficult, so they also know that you will make some mistakes... making mistakes is normal. Let me ask you a question. "If I spoke Mandarin to you, and I made a mistake, would you think that I was stupid?" I have tried to learn your language, and if you heard me speaking mandarin, you would see my mistakes, but you would be glad to see that I was trying hard to speak your language. One more thing to think about: You speak Mandarin 100% plus you may speak English 5% = 105%. I speak English 100% plus Mandarin 1% = 101%. So, who is better at languages? I wish I could speak Chinese as well as you speak English. Be proud of the English that you know and never be afraid.

You could write a few notebook entries, you can practise a lot by that; and when native speakers correct the mistakes, you can improve even more. Next time it will be much easier and you will be able to remember words without problems.

Practice more and more,never give up.if you do same thing for serval years, you can across any obstacle.