meticulous CSS/HTML update for better mobile experience. add new pages

Custom Order Request Hi! I need some meticulous HTML/CSS help with a client site (not WP). For [login to view URL]: 1. Clean-up the design and optimize the whole site for mobile without modifying the HTML too much (CSS if possible, it's a bit messy). 2. Build new HTML/CSS to make Cart, Checkout, "My Account" and "My tickets" pages responsive. 3. Replace Owl Slider with LayerSlider on the homepage 4. Integrate an h1 tag into each page for SEO purposes (but keep the design) ----------- Caveat: I don't have server access so all the work must be done on the original, static HTML/CSS files. The dev will integrate php code later. Most of the content is dynamic so the pages should scale well. The design overall is fine, but the new HTML was "updated" to an existing PHPIgnite site rather than built fresh. This is why the Cart, Checkout pages exist on the live site, but are not present in the new design. These need to be created. I'm a digital product manager and formerly a HTML/CSS guy myself so I should be able to answer questions. I did not code this site, it's a new project that I'm optimizing. Thanks!