BigCommerce Site Performance Review

I need a thorough review of my BigCommerce site's functionality and performance, specifically focusing on e-commerce and payment systems.

Key areas to assess:
- Payment gateway integrations
- Checkout process efficiency
- Any broken links or errors in the purchasing flow
- Overall site speed and responsiveness during transactions

Ideal Skills and Experience:
- Proven experience with BigCommerce
- Strong background in e-commerce site functionality
- Familiarity with various payment systems and gateways
- Ability to provide actionable insights and recommendations for improvements