Website Upgrade with E-commerce

I need an experienced web developer to upgrade my existing site by adding e-commerce functionality.

The site will primarily be used to sell services.

Key requirements include:
- User-friendly e-commerce integration
- Secure payment gateway
- Service listing and categorization
- User login and registration
- Mobile-responsive design

Ideal skills and experience:
- Proven e-commerce development expertise
- Strong understanding of UX/UI design
- Familiarity with secure payment systems
- Experience with service-based selling platforms

Please provide examples of previous work.