You need to set the character reference with the character you wish it to point to.
If I say the word “Ball”, you’re probably thinking of a round bouncy thing, because those are (often) their properties.
If I say the word “Ball” in a room filled with balls, you’re going to ask me “well, which one?”.
If I say the word “Ball” and point at a ball, then you know which one I am referencing.
Your variable gives you access to all the properties that class has, but without a valid reference it’s not very useful.
There are many ways to set a reference and how you go about it depends. For example the widget, if you create it inside the character blueprint, then all you need to do is to expose the variable inside the widget and pass in a “self” node when you create the widget.
If you are creating it anywhere else, perhaps the player controller, then a more elaborate method is needed. Maybe (get controlled pawn) - (cast to [character]).
In the case of the overlap trigger, you need to take the actor pin and cast it to “vocé”.