If you're trying to improve your English, I don't recommend calling anyone dude. Some people use it, but they do so knowing how it sounds and will be received. It can come across as trying too hard, depending on who's saying it. Others don't give an eff, and say it anyway, and that works too.

eta: I went to school in Norway for a bit and there was a teacher who had an American slang notebook that he would add to whenever he met an American. The problem was, most of what he had in his book was out dated and he just sounded weird when he used the terms.