jimmy wrote:yes,you are right that I need to improve my language for professional english.
but here more than studying,I need to concentrate on how to study. because I experienced that it is a bit time consuming.
for instance ,because of some various reasons;I am not sure which of these will be better for selection
*** a course center
*** self study.
I would point out that I am supporting contemporary educational system.
Here's what I've noticed: self-study is very effective if 1. you know how to self-study, and 2. you know how you learn. For some people these things are obvious and they can apply them effectively, and then there's the rest of us that are still trying to figure it out. For example, I'm finding that I have strong spatial memory, so using calligraphy makes sense for me to remember Japanese characters because I remember the size of the stroke in relation to another stroke.
If you're not sure how to self-study, then a course, or a knowledgeable tutor, will be necessary. They will give you feedback on what needs to be improved, and will guide you on your language journey. I say "guide", because as Zenmonkey says, it's up to you to remember all that they teach you--you are not a passive sponge.