FAQ Accordion with SASS and NO Javascript

Does anyone know how to get the box-shadow right? I'm not satisfied with the solution I came up with regarding the bottom shadows and I also noticed that the cube also seems to have it's own shadow that spills into the original image. I tried quite a few things but didn't manage to get just like in the original design.

Does anyone have any ideas how to manage those?

Any advice would be much apreciated, thank you!