Before I offer my corrections, I have to say your English is already better than most of my friends' English!

The reasons why I want to perfect English (and in this context pronounce "perfect" as "pr FEKT" not "PERRRR fect" -) 

There are some reasons why I want to perfect my English: firstly, I am interested in English very much. I want to continue to develop basic English competencies and cultivate the capacity for lifelong learning. Secondly, learning English can expand my horizons.(insert a space)I hope to open my mind and develop a positive attitude towards the native speakers and their culture.(insert a space - 2nd time you've done that, is it something to remember?)Plus, I would like to make more ("make more" is slightly awkward on the lips!) new friends who also enjoy learning, from all over the world. Last but not least, I want to get my have job satisfaction, it means something to me.

xjwfy2011 it may seem like there are a lot of mistakes in there, but really there are not. 

Your English is superb! if anything, a little formal and business like. If I wrote your statement, I would say something like, "The reasons I want to perfect my English. There are reasons why I wish to perfect my English: firstly, I love the language very much, I want to take what I already know and improve upon it hopefully with a view to lifelong learning. Secondly, learning English can expand my horizons. I want to develop a positive attitute towards native speakers and their culture. I would also enjoy making new friends from all over the world, who perhaps share my enthusiam for learning. Last but not least I want job satisfaction, it means a lot to me.

Something like that :) your statement would be good in a business meeting, mine would be good in a language lesson in a cafe.

I say you should write, "perfect my English" because you have already learnt English very well.

Well done.

Craig