When I speak I use a small vocabulary, even though I know a lot more than that. Those words tend to be vague and boring. I know other alternatives for those words, although it doesn't come out naturally. I always resort to those vocabulary that I always use.
Another problem is that I always stumble when speaking. I felt like I don't know how to control a conversation. I don't know how can I make my speech flow smoothly.
Is there anything I could do to improve my natural diction?