Graphics Programming?

I have two questions

  1. How can i create new custom shaders?
    2.I have one more problem that i am not able to figure it out which is if I want to modify functionality of Deferred Shading,Lit Translucency etc - https://docs.unrealengine.com/latest...iew/index.html - Is that possible ?If yes then how - where is source code for doing these type of things?

I guess the answer to this is - https://forums.unrealengine.com/showthread.php?56359-How-can-I-get-to-C-Implementation-Help!!