Image in design mode different to preview mode - help

I’m new to webflow. I’m sure this is a simple question to answer for anyone with some website skills…i’m also new to that too. My general layout on each page is a background image with text over, including nav bar. I’ve have tried to figure out what size the image should be (that’s a feat in itself…) and think I got it right until I look at it in preview mode. It changes dramatically. Positioned where I want it in designer mode, in most cases it zooms in and cuts off the bottom. What do I need to do to keep the design mode image?
(I think I shared the read only link to my site correctly…again newbie at this…)

Here is my site Read-Only: LINK
(how to share your site Read-Only link)