OpenCart Malware Cleanup Specialist Needed Urgently

I need an experienced PHP/OpenCart malware cleanup specialist to help fix an infected OpenCart ecommerce store.

Site details:

* OpenCart version: 3.0.3.3
* Dedicated server
* SSH and SFTP access available
* OpenCart admin access available
* No recent extensions or major changes added
* Store will be migrated to Shopify in 1–2 months, so this is cleanup/stabilization only

Issue:

* Visitors are randomly redirected to suspicious/malicious pages
* Redirect does not happen every time
* Redirect happens more often when users visit the cart or add products to cart
* Admin area appears normal
* Antivirus/browser security tools are showing dangerous site warnings
* Issue first appeared around late April, stopped for a while, and has now returned

Required work:

* Identify the exact redirect source
* Check OpenCart core/startup files, catalog/controller files, theme files, JavaScript assets, .htaccess, config files, database content, cron jobs, server logs, and writable folders
* Search for obfuscated PHP, eval/base64_decode/gzinflate code, hidden backdoors, injected scripts, suspicious remote URLs, unauthorized files, and reinfection mechanisms
* Remove malware/backdoors
* Prevent immediate reinfection as much as possible
* Verify storefront, product page, add-to-cart, cart, and PayPal checkout flow
* Provide a short report of what was found and changed

Important:

* Do not rebuild or upgrade the store unless approved
* Do not delete business/order/customer data
* Backup or confirm backup before risky changes

Please apply only if you have real experience with PHP/OpenCart malware cleanup, hacked website recovery, or redirect malware removal.

In your reply, include:

1. Similar malware cleanup experience
2. Your first steps for this issue
3. Estimated fixed price
4. Estimated time to complete
5. When you can start