How Can I Speak to English Beginners?

We got a question from one of our listeners here and that's where this topic started off from. Michelle, could you go ahead and read the question? We don't have the listeners name, unfortunately, but we'll go ahead and just read the question. I've been living in the US for six years, but I had been surrounded by native speakers. The only issue for me was to speak fluently or use the right expressions. But recently I'm exposed to more diverse environments and I need to communicate with colleagues who just came from foreign countries. How can I speak to English beginners clearly, nice and nicely, but not make them offended?