Changing background picture size for mobile

Site URL: https://itismichaelangelo.com/group-program

Hey guys, my header background looks great on desktop, but it does not fit at all on mobile. Is there some CSS code I can use to have the background picture be formatted to fit on mobile?

Try this 

<style>
  @media screen and (max-width:640px) {
  img {
    object-fit: contain !important;
}
  }
</style>