Your PHP version (version 5.6.40 ) is not compatible with some plugins, so it throws an error when you update the plugin. I had to disable these plugins in order for the website to continue working.
Please update your PHP version to 7.3 or 7.4 for compatibility with website plugins.
After updating PHP version, let me know so I can check other parts of your website.
Your theme is so old that we no longer support it.
I have tried to edit a few details so that the website can continue to work, but there are still many problems with your website if you update the plugin + theme.