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I have tried changing the image size of my banner image to look like the demo site – I want it to go across the page and maybe with a grey bar on the left and right (border)

the original size is 1410 x 797.
I have tried
1600 x 904
1920 x 1085 – this looks the best, although I lose part of the bottom of the image.

I just want my image to look central to the page, no matter what the computer screen resolution (currently 1920×1080)
Can we adjust it some why to use percentage rather than pixels???

The page I need help with: [log in to see the link]