BP casting variable issue

Hi there, i´ve got an issue here with the handover of my variables. I know my casting skills arent perfect but I´ve always managed to get my variables over until know. I have a widget called “shop” where i Change my index value of the brush i want to use. this value is form another widget called menu. I´ve tested if it Fails, but it doesn´t. The value is used to get an brush from an index which is in a Bindung to the Background image of my main widget. the node where i Change the sky´s material is working fine but why not this simple Image Setup? this is an important step and i appreciate every offer
thank you.

figured it out by myself