Hi there,

You can study whatever you want to learn nowadays.

Since everything is available on web you just need to simply select from whom you want tk learn and also what you want to become. See, nowadays a student can leave everything that he/she can learned from university.

Simply search  the medium in which you want to learn. Since, you have mentioned that how to join class free of cost. Simply make a structure of topics about twhich you want to learn and type on Google watch YouTube videos,make notes and bang on.

Hope you got my point.

Thank you and revert if you feel any doubt.

Good luck!!