Shopify Store Overhaul

I need experienced Shopify developers to help overhaul our e-commerce website.

Key requirements:
- Improve user interface design, loading speed, and mobile responsiveness.
- Work with a pre-purchased Shopify theme.

Ideal Skills and Experience:
- Proficiency in Shopify development.
- Strong UI/UX design skills.
- Experience with theme customization and CSS editing.
- Ability to optimize site performance for speed and responsiveness.

Please provide a portfolio showcasing similar projects.