Hello,
1/ Provide URL of your site and temporary wp-admin access, so we can take a closer look.
2/ To disable categories, add the next code in Theme Options > Theme custom CSS > Global:
.ajax-search-form .ajax-search-categories, .ajax-search-form .ajax-extra-content {
display: none;
}
@media only screen and (min-width: 993px){
.search-full-width .et-mini-content {
height: 300px;
}
}
Regards