To Chang:-
---How to improve and learn your English including Grammar, which is bad, especially tenses?
---Try buy a book called "The OXFORD study Thesaurus" published by OXFORD University press..
---You have synonym--antonym--12 tenses of a verb---future, imperfect, past, perfect ,pluperfect, present etc.
----->in both Chinese / English linguistic terms for you to savoury.