OpenCart Cleanup & Upgrade

My OpenCart store is showing its age. I’m looking for someone to bring it back to full health and move it onto the latest stable OpenCart release.

Here’s what I need handled:

• Fix the obvious pains: broken links across the catalogue, pages that crawl instead of load, and the persistent error messages currently appearing on the front end and in the admin panel.
• Upgrade the entire site to the most recent OpenCart version, carrying over the existing theme, products, orders, and customer data.
• Take a comprehensive backup before you touch anything—I’m not certain which method is best, so please advise and execute the safest option.
• Audit installed extensions; let me know which ones are essential, which might break during the upgrade, and suggest replacements if any are abandoned.
• After the upgrade, test all key user journeys (browse, add-to-cart, checkout, admin order processing) and confirm that speed and stability are improved.

A concise changelog and quick hand-over notes at the end will be appreciated so I can track what was fixed or updated.