Hello,
It looks that one of the third-party plugins that you use causes an error with the DB http://prntscr.com/t8chf2 and site is down http://prntscr.com/t8ci4c every time we try to go to any backend link. So, I have disabled the mentioned plugin. Contact plugin author and solve the problem. By the way, we would recommend you to check the list of plugins that you keep enabled and disabled those plugins that you don’t really use. Don’t keep plugin enabled just in case because every additional plugin slows down the site.
1) The green background appears because of custom http://prntscr.com/t8cqgq I have removed classes that caused issue for the add to cart button. Check now.
2) Read this post https://www.guypo.com/introducing-lqip-low-quality-image-placeholders#:~:text=On%20one%20hand%2C%20images%20account,byte%2Dwise)%20as%20possible.
Regards