Almost, make sure to create the boolean inside the game instance:
Also make sure your game instance is set in the project settings (Search game instance and set the object).
Then when casting from the game instance like you already are, from the output set the boolean “Was Overlapped” to true.
Get rid of the get all widgets of class and everything after it because you want to do that from inside the widget when it gets added to the viewport. So from inside the widget, on construct, run the set visibility to the boolean from get game instance.