Fylo landing page with two column layout using SASS

First i was wondering how do you add the " Please check your email " on the input when the email is not the right format ? ::before and ::after doesn't work on input tags, and to my knowledge It is not possible to style a parent on child hover (or :invalid in my case) so I am stuck.

Second of all I know my code is very sloppy and I feel kind of bad for putting it out there :). When looking at the design I thought about going in a certain direction, turned out to not be so good and instead of redoing my html and the first part of my css I justed pushed on and kind of brute forced my way out.

I want to keep pushing on challenges with HTML / CSS only to soon start working and learning JS which I am excited about, and will later come back to this challenge and fix my solution.