@Geeraffeman: Further to the advice offered by @mallcop32, my first thought was that your issue could be related to Smart Pop Up View. With this in mind, head to Settings > Advanced Features > Smart Pop Up View, and toggle off Whatsapp to see if this helps. You can also try heading to Settings > Apps > Whatsapp > Notifications > Select a notification sub heading > Show as pop up > Off.
they should fix this bug asap.
waste of money for a flagship phone.
the video above is a guide how to temporarily fix note 9 yellow screen discoloration.
1. turn on always on display in settings.
2. tap screen to show clock, then open the phone.
credits to the video maker who manage to find the temporary fix.