Good day
To insert an image banner into your Shopify website’s header, I can modify your theme’s code. I can use CSS media queries to ensure the banner only displays on mobile devices. The banner can be hidden when the device is rotated by using the orientation media feature in your CSS. The code for the banner will be located in your theme’s CSS file, which you can access and modify through the Shopify admin interface.
I've hands on experience in Shopify development, HTML, CSS (Bootstrap), JavaScript, jQuery, Shopify Liquid, Shopify Templates, custom theme development and expert in bug fixing and troubleshooting Shopify sites.
It would be great if we can discuss further regarding job in chat so that we can take the next step.