One app is stuck, and appears on all others even when i scroll.

Thanks for the screenshot, it makes the problem clear: the Gmail notification is drawn on top of the app list and stays in place while the list scrolls underneath it.

The closest thread we have is Persistent notification overlay stuck on the home screen (In Review), where a notification preview also stays visible over other elements after it has been read or dismissed. Upvoting it keeps the reports together and gets you updates.

As a stopgap, users seeing a similar leftover notification row report that restarting Niagara clears it for a while (Android settings > Apps > Niagara Launcher > Force stop). If yours survives that, please say so here in the thread, that would be new information for us.