Hi,
The warning is something we've reported to PHP :
github.com/php/php-src/issues/8251
The issue is still open. If you can update to PHP 8.2, you would get a warning message with more accurate information which would help us explain to the PHP developers in what circumstances the issue happens.
Regarding the fatal error, it says that you have a memory limit of around 90M configured in your php.ini and that Joomla/HikaShop/the other extensions loaded on the page need more memory to run the processing of the page.
90MB is not low, but it's not high either. The default in recent versions of PHP is 128M and it's not uncommon to increase this to 256M. So I would recommend first trying to increase the memory limit of your PHP and see if that helps.
If it does, then it's just that, there is too much data in memory for that page processing and keep it increased.
If you still get the same issue after doubling the memory limit, then it's likely another issue, like an infinite loop eating more and more memory until it reaches the maximum allowed. In that case, we'll likely need a backend access and a FTP access in order to investigate what's going on.