Big Cartel Store Optimization, Ux Improvements & Landing Page

We are looking for a freelance web developer to optimize the Big Cartel online store of a French painter, as part of the development of her artistic brand. The site already exists. We do not wish to rebuild it, but to improve its user experience, aesthetics, and commercial effectiveness. Requested tasks: 1. Improve ergonomics and navigation, especially on mobile. 2. Clarify the presentation of different offers: original artworks, personalized portraits, and reproductions (prints). 3. Add or optimize call-to-action (CTA) buttons: order a portrait, discover artworks, contact the artist. 4. Customize certain automatic mentions, notably 'Limited Stock', where Big Cartel's technical possibilities allow. 5. Improve the presentation of product pages and the visibility of commercial information. 6. Create an elegant and responsive landing page presenting the artist's universe, her works, and services, accessible via QR code and linking to relevant pages of the site. 7. Verify graphic consistency and proper functioning on desktop and smartphone. We are looking for a professional proficient in html/css, ideally with experience in customizing big cartel stores. Please provide: - A detailed fixed-price quote, distinguishing between site optimizations and the landing page. - A completion timeframe. - Examples of similar work. - Confirmation of technical possibilities and limitations on Big Cartel. One-time mission, with possibility of future collaboration. Quick start desired.