MAGENTO 2.4.3 + front end

I need a senior Magento 2 developer who has previously worked with:
• Magento 2.4.3-p3

WHAT MUST BE FIXED
1. Add to Cart fails randomly.
3. iOS Safari: page cannot scroll or interact.
4. Chat bubble overlay appears on product page and checkout.
5. Payment fields positioned incorrectly (appear above address fields).
6. Two page-load errors appear on every page.
7. Banner script triggers repeatedly (every 0.5s) causing multiple errors.
8. Mobile reviews duplicated; layout overlaps and chat covers text.
9. Success page styling incorrect: background wrong, button colours wrong, missing shadow.
10. Banner spacing incorrect: needs automatic spacing depending on banner visibility.
11. Banner not full-width.
12. API is applying the coupon code second time gives wrong price