First, thanks for considering to contribute to this project. Please feel free to contribute to the quality of this content by submitting PR's for improving the explanations or code examples. If you want to ask about a particular chapter with confusing explanation, please open an issue first and ask about it.
A merged PR will make you appear in the contributor list. The content will be considered a donation of your work to this project. You are still bound by the conditions of the license, meaning that you are not considered an author or owner of the content once it has been merged in.
You can always open an issue for confusing explanation or any other JavaScript question concerning web development. I will not be able to give answer to JavaScript questions concerning, say, the building of IoT application and machine learning. But if you're stuck on a particular exercise or project, I would recommend you to go and look for the answer in StackOverflow, the best website to look for coding solution on the Internet.
Also, you can suggest new topics that needs to be covered, as I'm actively trying to add more content to the book. I will consider them in the next update of the book.