Hello,
I have tested your site. There is a bit of a space at the top in the mobile screen. It seems the space is due to your custom code. Kindly undo your custom code and then check back.
OR
You can use the below CSS code in Theme Settings >> Custom CSS >> Custom CSS for mobile:
.whb-clone .whb-general-header-inner {
margin-top: -5px;
}
As you want to edit the layout of my account page, checkout page and bill form. These are related to default WooCommerce. So you can’t edit them directly with the page builder. You need to use custom code or third party plugins to modify those pages.
Best Regards.