Opacity on scroll

Hi everyone! I am trying to create a opacity scroller like they have under “Why Kishu” on this website: https://kishu.com/

Does anyone know how to do it? When I try to do it with my opacity trigger, they does not go from 100%-0% while scrolling, but instead they are fading into one another.

i also would like to know, using the webflow checker, this website was made in webflow too, so its certainly possible