Close popup before menu is active again

i’m working on a project where i would like to build a menu of 3 buttons in the bottom of my screen, when 1 of these buttons is clicked a little popup MC pops up with a X sign to close it. WHen the popup is active the background (the buttons) fade to a 30% alpha and a re not clickable anymore. When i close the popup MC with the X sign then the buttons are active again. I seen a tutorial how to do this but i lost it. Can someone help me out with some info please.

Thanks in advance