Improve oral skill, any suggestion ?

My personal experience is that the only effective way is to consistently engage in English conversation. Watdhing English programs helps but until you're able to practise your skill, there is a limit to what you can achieve. Years ago, a friend from HK was doing a marvelous job translating English to Cantonese during speeches by Americans. I'd always felt she would be a great orator in English until I heard her speak one day. Her accent was so heavy that it was even hard for me to understand. Many who are proficient in reading, writing, and listening English may not be as good speaking it. For those who don't have English speaking foreigners in their neighborhood, it may be helpful if you can find those in your circle who are willing to speak to one another in English.