Joomla Upgrade and PHP Update

We are seeking an experienced Joomla and PHP developer to upgrade our websites to the latest versions. Our sites are currently running Joomla 3.8.5 with PHP 5.6 and require an upgrade to Joomla 3.9.x and PHP 7.2 to keep them secure and enable new features. The project involves testing the upgrade process on a staging server, addressing any compatibility issues, then deploying the new versions to our live production sites. Full documentation of the configuration and any customizations made is necessary. Cross-browser and cross-device compatibility must be validated along with all plugins, modules and templates functioning as intended. Security best practices such as leveraging HTTPS and strong passwords should be implemented. Once complete, the sites should be optimized for performance. The developer should have extensive experience upgrading Joomla and PHP versions for live client sites. Professionalism, communication and delivering high quality code according to best practices are essential. We seek a skilled developer who can successfully complete this upgrade within our scheduled timeframe.