Viewport Size and Screen Resolution Different Issue

Hi,

I’ve been setting up my settings menu using blueprints and noticed that when I set my screen resolution to my desired value the viewport size is different and there are black lines to the side of the game as a result and anyone know why this happens and how I can have my viewport size and screen size match?

Also, I noticed that when I play my game in standalone mode the window does not resize based on my resolution but when I play in the new editor window it does not sure why