Hello Legas Games,
I suggest watching this tutorial to see how to do the UMG progress bar itself:
As far as setting up the logic for the Stamina itself, you can deplete it like they do with Energy in that video tutorial. The only difference is that you’ll need to set the FirstPersonCharacter blueprint to check for when Stamina is <= (less than or equal to) zero. When it is, you can change the variable called “Max Walk Speed” in the CharacterMovement component to any value you wish.
Hope this helps!