Well, those are created with renders and/or stocks (already created characters and cut out) then put in a canvas (clear photoshop layer) and then it was painted and spammed with special effects.

It shouldn't take you too long to learn how to do this, maybe 2-3 weeks. If you want to do some overall art working I would suggest going to YouTube and learning how to use the software of your choosing, then type up "How to make signature tutorials" and learn what is what and what can be done.

For the rest...well, those are a bit more advanced like CGI and 3D modeling. One thing I have to ask though, do you know how to draw and or are skilled/talented? Don't be modest lol