when a button is pressed other button is disabled, I want to save the button state and when I load back it should be disabled and vice versa.
You should use game instance, Event Constrcut > Get Game Instance > Get button style and when you pressed OnClicked > Get Game Instance > Set button style.
(the Set button style can be a simple Enum with a Switch)
and your save system should save/load your button when you exit/autosave your game (unless you want it only during ingame).