Apply :before and :nth-child on li?

Question

css

There is a task between menu items to put "squares". Done now via the :before pseudo-element, but now I need to remove the "square" from the first element? What am I doing wrong or what is the best way to implement this?
Example here:
codepen.io/unionfourman/pen/zvpbQN

Answer 1

On line 9
li a:first-child:before