Hi I want to be an English teacher but I am not very confident in my writings. How can I improve that plz. Thanks

Start by putting a capital E on English!

To become a good writer, you need to read, read, read, and write, write, write.

http://als.lib.wi.us/Collegebound.html
Read everything you can get your hands on. Many of these works are available in full online; others you'd need to check out from your library or buy from a bookstore.
Here are some places where you can search titles to see if they're available online:
http://books.google.com
and
http://www.gutenberg.net

http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=journal+writing
Write as much as you can -- keep a personal journal, which can include your thoughts and responses to books, stories, poems, plays, etc., that you read.

Read, read, read.

Write, write, write.