dialogue box in dashboard

Hi,
I’ve accidentally turned off the dialogue box that requires confirmation of stuff in the WP backend – which means now I’m unable to perform a whole bunch of crucial actions!
I’m talking about the box that pops up if you want to delete something in the media library, or if you try to leave a page without saving.
Unfortunately, Visual Composer also uses these boxes to confirm if you want to delete an element in the page builder. This means I’m stuck with stuff on my page that I can’t delete!
Please help?!