Interview For An Internship

I went to a textile company to have an interview for an internship and applied for a foreign trade merchandiser. During the interview, the interview asked me about my career plan. I told her I wanted to become an overseas sales manager.
And now since I don't have any relevant experience and skill, so I need to start at the bottom. I am worried something bad will happen.
In fact, I am a senior student whose major is Japanese, but I hope I can do some English-related work, because it would help to broaden my horizons、meet more people from various countries and improve my commercial English ability.
From today on, I know I need to recite more commercial vocabulary and learn how to write a good business email.
Work hard！No matter how difficult it is.
Finally, I want to ask how to improve my oral English, just like how did you study chinese?