Scrollable image over static image

Alright, I’ve got a doozy for you all today. I have a long image in a scrollable div box, but it’s a web page image, so what I’d love is to place that scrollable image over a laptop mockup so it looks like you’re scrolling the web page on the laptop screen. Not only am I not sure how to do that (setting the mockup as background? As an image at -1 index?), but how to ensure that the positioning stays consistent responsively. Any thoughts would be immensely appreciated!

Here is my site Read-Only: LINK
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Is this what you’re looking for?

Hi Jacie,
I’m not sure why, but I never got a notification when you responded, so I apologize for the delay and really appreciate it, because this is exactly what I’m looking for. Thanks again!