Sylius Developer needed: Technical Upgrade from Sylius 1.2 / PHP 7.2 to Latest Stable Version

Hi! I am looking for an experienced PHP / Symfony developer to perform a major technical upgrade on my ecommerce store: blexen.com. The following is what AI wrote, I am not a specialist. So do not drop because of partly AI text. Current Issues: Before the upgrade, you should know that we currently face two specific issues: 1. Category Bug: We currently cannot create new categories. This seems to be a known issue in this older version. 2. Performance: The shop is currently loading very slowly. Scope of Work: This is a purely technical migration and optimization. We do NOT need a frontend redesign, and we do NOT want to add any new features. Your sole responsibility is to bring the framework and dependencies up to date, fix the existing bugs mentioned above, ensure complete database compatibility, and achieve a stable, fast deployment. Key Responsibilities: • Perform a step-by-step upgrade path of the Sylius ecosystem (for example: from 1.2 to 1.3 and up to the latest stable release). • Resolve any deprecated Symfony components or third-party bundle conflicts. • Ensure smooth data and database migration without losing any order, product, or customer data. • Set up a staging/test environment first to thoroughly test the checkout flow and payment gateways before pushing to production. Requirements: • Deep, proven experience with Symfony and the Sylius framework. • Strong understanding of modern PHP 8.x features and backward compatibility challenges. • Experience with Composer dependency management and MySQL database migrations. • Fluent in English and capable of working independently. How to Apply: Please start your application with the word SYLIUS-UPGRADE so I know you have read the full description and are not using an automated AI bot. In your proposal, please state: 1. Have you handled a major Sylius or Symfony framework upgrade before? 2. What is your estimated timeline or hourly rate for a project like this?