Make pop up truly responsive?

Hi there,

Is there a way to have the pop up be truly responsive? For example, we would like the window to display a little larger on larger screens and then shrink to fit mobile screens appropriately. If we place an image within the pop up content, that image isn’t responsive like images placed within our regular pages is on mobile (in other words, a 600px wide image remains that size no matter what the screensize is). Is there a way to make this more responsive/mobile friendly?

Thanks

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