Version 5.2.2.1 is a very old legacy codebase, it is possible to upgrade sequentially to 5.6.4.0 and this will work on php7.4.
It is not a straight forward process though and if your site is not too big it would be easier to rebuild on the latest version.
Unfortunately, it depends on what version of concrete you are currently running as to how you preform the upgrade process,
If your site is not working and you cannot set the php version of your server to one lower than php7 then it needs to be performed using a local web server with various versions of php available.
Ideally, restore your site to a working previous version from a backup. With a failed update from (unknown) to (unknown), it is unlikely that anyone will be able to give you instructions through the forum.