It is not about numbers. This is the same line of questioning I have heard for four friggin years. There is no shortcut to proficiency and there is no magic number for vocab after which you will understand English. It doesn't work like that.

Best advice I can give to you would be this: read, read, and read some more. And when you come to a word that you are unsure of, don't just pass it up. Go and look it up in the dictionary. That is probably one of the best, if not, the best way to improve your vocabulary.

i've tried read more and i think i can understand you well.but as soon as i wrote something in english(such as post a thread in the forum), i feel it is just something different from your 'native' english,which really bothers me.
i know there is no shortcut to proficiency and the correct way is to do more reading,listening and writing,and i really want i can share your experenice.

Don't worry about it MYH. "Face" or "pride" are major obstacles to learning so if you can let that go you will be free to challenge yourself, grow and improve. Now, no more fishing for compliments, get out there and write.

Hooked on Phonics worked for me! But seriously, the way I learned(besides listening to grown-up. Was reading. Reading would be the biggest one for me. I enjoy it and it helps improve the vocabulary. Find a genre you like and go with it. I myself have read every Dean Koontz book that my public library has to offer...Read. simple.Our 'native' english would just be our accents. Thats probably it. For example, when I go to my aunts house in Pennsylvania, I have to change the word Coke to Pop. Any type of soda for us in the South is Coke, whereas up north, its Pop. Thats probably why you feel differently.

also, try to speak it as much as possible. i took alot of German, and i try to talk to my dad in it alot, to keep up my proficiency. reading helps with writing, but its still really hard. ive done alot of translating German, and im still not very good at the writing part.

Get some basic knowlegde of the "language-tree" you`ll see that for example language such as french, latin and english is in the same branch. That basic knowlegde, makes language study much easier.

Waching english TV with our own subtitles also help ALOT... Most Norwegians kids can speak english "fluent" before they start learning it at school because of TV..