Hello,
Lazy load option for the images you can find in Theme Options > Speed Optimization > Images.
We don’t have Lazy load option for all, only for the images and product elements in the WPBakery Product element settings.
Try to optimize the images on your site using the Tinypng service. At this moment images on the home page takes 3.4 MB http://prntscr.com/uztaiu and it gives not good results http://prntscr.com/uztbvs
Regards