Need help for getting started

Hello all, I am a newbie here. I'd like to contribute in architectures, kernel features, virtualization, and drivers parts, but I don't know where is a good way to start. I have looked for some advice but I have had a hard time to understand (Some advice is too general. Some used too old kernel versions, so I cannot catch up when reading the newer ones). I learned about OS, C language, and assembly language. I can configure and build the kernel. Would someone guide me where should I start? I appreciate for your helping. Sorry if there are some errors in my writing, because English is not my native language.