Silverobama, your response to Skrej does a much better job at explaining the situation and context. A lot of the nuances you just described were unclear from your initial post here, which is why it came across as rambling and repetitive (Rover_KE), boastful or self-aggrandizing (Skrej), and unsubstantiated in its conclusion (Tarheel). It felt like some of what you were saying didn't have a point, which in hindsight wasn't true. Rather, because your points weren't clearly tied together and you didn't give enough details/context, it didn't guide readers effectively into understanding the intention/relevance/meaning behind the different parts of what you said. Going back and reading it again now that I have more context, I can better understand what you were trying to communicate.
Clear communication is a challenge even for native speakers of course. You are clearly capable of it. Your second message gets your points across in a way I can understand and agree with, and doesn't suffer from any of the original problems others described.
However, it has a new problem. It comes across a bit defensively, with lines like "I know why you don't understand this", "I don't know how to explain this because it's such a long story that I can talk about it for a week", and "Feel free to visit China and join our English club." That last sentence even seems a bit passive aggressive.
The other reason why it seems defensive is because you jump into telling more of your story without first explaining why you are doing so. By the end, it is clear that you are trying to help us understand by giving more context, but that's not obvious up front.
Instead of "I know why you don't understand this, Skrej", I'd recommend something like this: "I was being modest when I said 'I don't think so'. I actually do think I'm pretty good with spoken English, though obviously I have room to improve. But it's clear based on your responses here that I might not have explained things well, so let me try to provide more context below."
Good luck with your talk! It sounds like you will have a lot of advice that will be helpful for your audience.