How to link pop-up modals to CMS data

I have a collection list displaying on my website, each of the list items has a button which opens a pop-up modal. The modal I’m using is this pre-built one from memberstack:

I want to add cms content to this modal specific to the collection list item that the button is in. For example click on “Open invitation” and the pop up displays an image from that collection list item.

I can get it to show collection list data but it seems to be showing the entire list and overlaying the data on top of eachother (see screenshot).

How can I get it to show text/images from the correct collection list item?
Thank you

Here is my public share link: LINK
(how to access public share link)

Here’s a guide + cloneable;