How to learn game development?(PC and Mobile) [on hold]

I am an electronic undergraduate and none of my friends even in CS have idea how to become an independent game Dev or even work as a product engg./game Dev in a mobile based gaming startup.Sure they know full stack mobile app development is one part(on mobile),also working on some engine like Unity etc, but nothing more.Any idea what things are important and also some advice to non CS background guys on how to start?