Joomla! 3 will continue to be provided with updates until August 2023, after which official support will end. Operating a Joomla! version that is no longer supported can cause problems, for example if security vulnerabilities occur for which no updates are then provided.
Therefore, upgrade your Joomla! website to Joomla! 4 to continue to receive updates and support.
You do not want to upgrade to Joomla! 4 yourself?
I will gladly do it for you! Benefit from my experience through numerous successfully performed Joomla! 4 upgrades.