Shopping Cart Functionality Fix

I'm experiencing a recurring issue with the shopping cart on my website. Specifically, whenever an item is updated in the cart, it only loads without any response for a significant duration. I require a freelancer with a strong background in troubleshooting website functionality issues, specifically related to shopping cart operations and online payment systems, to resolve this. Key skills needed include:

- Advanced knowledge of website coding and debugging
- Experience with online payment systems
- Proven track record of similar projects
- Strong problem-solving skills
- Excellent communication and timely response