Responsive Intro component with sign up form using flexbox

Hi everyone, I will be glad if you look at my solution and find any suggestions.

Especially the validation part in the form and javascript. I haven't yet looked at the best way or good practice to do the validation in someone's solution or google, I thought to use it from my learning and once completed can look in these, but aside from that if you can suggest me from your knowledge I'd really appreciate it.

Thank you.