If you want to improve your Unreal Engine skills, it’s just a matter of learning, you don’t need to restrict yourself to just the learning materials provided by Epic themselves, there’s lots of tutorials and guides available along with online workshops from people that aren’t affiliated with Epic that are extremely useful.
If you wish to start teaching Unreal yourself it sounds like you want to work with Epic, that would likely mean getting hired by Epic in a position related to developing training materials. You should also consider other options though, for example you can develop learning videos that you post online, or find a way to teach your own online workshop. There’s also many universities that have game development programs that teach Unreal where you could work.