Hi @michiel
Here you can find the implementation example which you can import directly to your website. (If you don’t want to lose your current setup, try importing it on another website).
Go to Tag Manager → Settings → Import from file
2022-02-03 13-06-55 - Trigger groups (a873389d-987b-4f0b-a884-bd77f270882a).json (9.5 KB)
The most important thing is to create a data layer trigger for your actual tag based on two variables (scroll & time). See the screenshot below.