Split Screen
How can I stop the split screen from popping up when in Safari. I'm taking a class and mail keeps popping in as a split screen. It's not great for my comprehension. There must be a setting, but I sure can't find it.
From the Mission Control hover you mouse over the split screen and click the X—split them up and back to Desktop.
Quit both apps, open them one at a time and put each into full screen, at least the Mail app to get it out of the way.
https://support.apple.com/guide/mac-help/use-apps-in-split-view-mchl4fbe2921/mac
Use Mission Control on your Mac - Apple Support