It's not only about accent and pronunciation, also about knowledge and information in religion, culture and pop news etc. When working for Jewish company, you better know sth "kosher words"; when talking with Christian, you better know sth Bible stories, when hang out with young guys, better know who and what's the fashionest people and way. So, you have to learn all the time, what you have learn in Xin Dong Fang or any classes in China is far away "enough".