We have a forum so that people can ask NEW, or hard questions. That's why it's annoying to have people asking the same questions over and over. We're glad you're modifying your bike, and that you want to learn how to make it faster. However, you should try to do that learning on your own time instead of wasting our time with questions you could easily answer yourself with a minimal amount of effort. If you spend some time searching, and figure out most of the answer yourself. but need some further clarification, that's a fine thing to ask about. However, we are not your personal consultants, we're here to learn and discover new cooler things from each other, not answer questions we've answered so many times that we've ARCHIVED the answers so that we don't have to type them out any more. That's why you're getting flak from people.
That said, good luck with modifying your qt50. Installing an expansion chamber exhaust is always the simplest way to get the biggest performance out of a 2 stroke engine if it doesn't already have one. But before you start installing performance parts, you should make sure everything is running perfectly and tuned in on your stock setup. The skills you learn from tuning your stock bike will be invaluable as you add performance parts.