Hi there try adding 

header {
    position: relative !important;

}

in customizer -> additional CSS

this is the easiest, quickest solution.

Hi there, 

if the first solution is not suitable, hiding the logo on scroll is actually custom work. We can do it (for a fee) or I can provide guidelines on what needs to be changed - requires some programming knowledge.

I forwarded your other two tickets to our web designer.

Yes, interesting suggestion. It is indeed recommended to have the logo smaller so that it will scroll on the left side of the content.

The function to modify would be BackToTop() in /js/scripts.js

$(window).scroll(function() {    
var scroll = $(window).scrollTop();

if (scroll >= 300) {

$(".scrolltotop").addClass('page-up').removeClass('no-tooltip');
$("#page-action-holder-right").removeClass('no-tooltip');

} else {

$(".scrolltotop").removeClass('page-up').addClass('no-tooltip');
$("#page-action-holder-right").addClass('no-tooltip');
}
});

exactly when the 'back to top' arrow changes up to down or the other way around.

You have to show also the logo when you go to different page with AJAX (which does not load the entire page but the target html+CSS content in the initial page container).

Hi there,

Are you planning using our theme?

I recommend asking for a refund.

Thanks, I hope you find what you need.