Im unaccepting this not because it isnt a good answer, but because im still stuck 
could you look at this shader and explain whats going on? I followed a tutorial.
Edit
I removed the link as I found a better one. But Im so stuck trying to learn this new one its making me lose sleep.
Have you heard of this one, called the Sobel operator? it’s used for edge detection and I sort of get it but I dont understand how to implement it in Unreal.