Header overlaps page

Site URL: https://www.marcelkimble.com/

Hi,

I used a css code to install a fixed header for my Wells template. Unfortunately the header overlaps my page when you use a mobile device to visit the page.

My code:

@media screen and (max-width:640px) {
div#headerWrapper {
   position: fixed !important;
   top: 0 !important;
   left: 0 !important;
   right: 0 !important;
   background: white;
      background-repeat: no-repeat;
    background-size: contain;
    background-position: center center;
    width: 30px;
    height: 80px;
    display: inline-block;
    visibility: visible;
 
}
div#mobileNav {
  margin-top: 110px;
}
}
@media screen and (max-width:640px) {
#mobileNav {
    background: #a3a3a3;
    position: fixed;
    top: 5px;
    left: 0;
    right: 0;
    z-index: 999;
}
}

Thanks in advance!