I was just wandering if it would be possible to maintain a multiplayer game .exe if me and my 2 friends learnt only the c++ tutorial on this web. I know you need a database like MySQL to make it online.
Learning comes through a combination of (a) knowing and understanding the concepts of the language, and (b) lots of practice and experience, actually writing programs (or even modifying existing programs).
A tutorial, or a good book will help you with (a). Part (b) you have to do for yourself, there are no quick and easy shortcuts to gaining experience.
you would at the very least need to know how to use a graphics library (OpenGL, SFML, SDL, Allegro) and a networking library. once you do and you have a few months of experience you could probably make some really simple, really glitchy multiplayer game that works 32% of the time you launch it, but the tutorials on this site aren't enough.