I tried my best but I couldn't make the following theme full width/screen by editing the CSS or any other way. I'd be very much grateful if you could show me or give me a hint regarding this customization.

I need to remove the space between the theme header and the browser search bar. I need to change that only, else everything is good.

you might have different options than this picture, it depend on your theme and your page builder if you have one.

though, for more information about