Weight painting help

Please. I need help with weight painting. I can’t fix the problem with neck on my character as it always deforming poorly doesn’t matter what I do.

I’ve watched all of DanPro’s videos on it and I still can’t do it. I’ve watched other weight painting videos and I still can’t do it.

I simply don’t know to weight paint anything, it just feels completely random.

Here is the blend file:

Quad_help.blend (1.36 MB)

Please, any help would be greatly appreciated.

What do you mean by

it always deforming poorly doesn’t matter what I do.
. I have tried it i works just well how do want it to be deformed?
Just wondering why do you have ik constraint on the head?