What should I learn other than programming language, framework?

I have some free time after work and on weekends, nothing else to do. I want to learn something other than programming language or a new JS framework. I already know node, react, socket.io, redis, vue.js, angular, laravel and php. I want to learn some thing related to computer vision and machine learning but I have not good understanding of math behind ML and computer vision so I am really stuck here.