Here is my suggestion. I split your first sentence into two because you are writing reported speech. There are other ways to rephrase the rest of the paragraph, but I decided to remain as faithful to your original words as possible. I hope other contributors will jump in and offer their suggestions.
Once, a correspondent asked Steve Jobs to give him advice on how to create excellent products. His answer was "to focus." This concept has influenced a large number of companies. For example, in the Chinese cellphone market, many corporations have begun to focus on producing one excellent product every year. Two years ago, these companies produced 5 different kinds of cellphones a month.
- For Teachers