Mobile image sizing?

[jeffreym]

Hey guys, I am trying to increase the entire size of this picture so it takes up an entire mobile screen. I have tried resizing the images though it just changes the image not the entire section. This is what it looks like  at the moment on mobile though I want it to take up the entire screen including the section below it.

URL: Hygiadental.com
pw: angel 

[jeffreym]

Sorry, I do not understand your coding and help. It is extremely confusing and so many mixed things to do. I struggle to understand all your explanations.