Full page modal window within a collection item

Hi there!
I want to create an agenda with seperate agenda items in a CMS collection. The idea is that when you click on an item, a full page modal window will appear in which you can read the additional informate of the agenda item.

I tried to make this now, but the pop-up within the agenda item, shifts with the position of the agenda item itself… The modal window is set to absolute, 100 vh and vw, but since it has to be within the agenda-item, it doesn’t really work…

You can see it here : Agenda!

And an image of how the design of the pop-up should look for each agenda-item
Schermafbeelding 2021-08-11 om 16.32.47|645x500

Would highly appreciate any pointers on how to go about this.

thanks in advance, Hessel

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