Shopify Header Bug Fix

My Shopify store’s header has broken on both desktop and mobile, and sales are at risk until it’s fixed. I don’t yet know whether the fault sits in Liquid, CSS, JavaScript, or some combination, only that customers can’t reliably use the navigation and the layout looks wrong... (Budget: $30 - $250 USD, Jobs: CSS, Debugging, Frontend Development, HTML, JavaScript, Shopify Templates, Web Design, Web Development)