Slider z-index

Hello, im trying to use a div as an overlay for the slider, so i can have some text/images/menus over the slider that works as a changing background, but when i try to get the div over the slider it gets hidden, no matter what z-index im using, is there anyway i can achieve this?
url:
http://www.elbedroom.mx/pijama-fest/

https://wordpress.org/plugins/slider-image/