Hello Albert,
Thanks for asking. 
We do keep releasing update for Visual Composer as and when Plugin developer releases update. Please note that Visual Composer is a bundled plugin that comes with X Theme and is not owned by Themeco. Visual Composer is developed by WPBakery. I checked your website and can see that you are using latest supported version of Visual Composer 5.6.
Having said that if you have designed any page using Visual Composer then you have to keep Visual Composer active. However, if you haven’t designed any page using Visual Composer then you can deactivate and delete Visual Composer from Plugins > Installed Plugins.
Thanks.