proc_open() has been disabled for security reasons I'm trying to update Craft, but I'm getting an error while updating stating it's not possible to make a database backup. I've therefore gone for the suggestion to revert back instead of pushing on. Back in the CMS now when I try to create a backup manually (utilities-> database backup) it tells me: 

there was a problem backing up your database. Please check the logs. 

I've done that and it says this: 

2018-11-30 11:43:57 [-][1][-][error][yii\base\Exception] yii\base\Exception: Could not create backup: proc_open() has been disabled for security reasons in /home/bxrdvjsx/xxxxxx.de/vendor/craftcms/cms/src/controllers/UtilitiesController.php:382

Does anyone know how I can fix this? If it isn't obvious from my question I'm not very familiar with Craft and have inherited this website from the person who built it.
Your host has likely added proc_open to your php.ini file's disable_functions setting.

If you have access to it, you can remove it from that setting.  If not, you'll have to ask your host to do it.

You can see that Craft requires the PHP proc_* methods to be able to perform some operations here: https://docs.craftcms.com/v3/requirements.html#optional-php-methods-and-configurations