Tang Lei, Gary did the right thing to correct all the mistakes in your post and you need to take notice of his corrections.
There is just one thing that you need to be aware of, though, seeing you seem to be learning American English:
In British English - also used in Australia and New Zealand - the past of 'learn' is 'learnt'. But note that 'learnt' is not seen as acceptable in American English. An American teacher would consider 'learnt' to be wrong and would amend this to 'learned'.
And one final point. Do not write 'u'. This is not a word. Native English speakers find it irritating when learners write u instead of 'you' because this looks lazy and rude. If you want to thank someone, say 'Thank you'.