Hello, some people learn through reading, others through videos, I myself became better by doing, not only amxx but programming in general. You just need to define the method that most applies to you and stick to it; knowledge comes with time, as long you put some effort.
Try to create a plugin, even if it has already been done by someone. If you have doubts, google is your best friend. If you can't find a solution to your problem, ask in a forum, there are always those who like to help others.