You may write interesting and informative articles, but unfortunately your English grammar needs work. The person who approved your articles the first time must have changed his mind. Here are some examples of English mistakes in your question:
You wrote "I receive some nice comments." It should be "I received some nice comments."
You wrote "...denied my articles and ask me improve my articles before submit." It should be "...denied my articles and asked me to improve my articles before I resubmit."
You wrote "Why deny after approved?" It should be "Why did they deny after approving?"
Do you see where I fixed your grammar? Infobarrel isn't a site for practicing English. Your articles must be grammatically correct before they go live. I hope you can find a person to help you edit your future submissions.