foreign friends feel difficult to understand what i say

Listen to as much English as you can. Listen to English-language movies. Listen to English-language radio. Listen to your English-speaking friends. You can't sing a song until you've heard it first...

I would be willing to help you with pronunciation through Skype, but I don't know any Chinese! my Skype is jazz.steck

Practice, practice, practice. Listen to native speakers as much as possible. Try to imitate their pronunciation. When foreign friends don't understand what you say, be willing to ask them to correct your pronunciation. They may already be doing it indirectly by repeating back what they think you said. But really the only way to improve your pronunciation is to know where you have problems and practice. It might help to make sure you hear each sound correctly. You can't imitate a sound if you can't properly hear it and distinguish it from other sounds. Here is a good one to get started: http://www.learnenglishfeelgood.com/listening/english-listening-test1.html

skype with someone a few times and see if they will be patient with understanding your pronunciation. My skype is Kaydub02 but I am not on that often... I will try to help if I am though!