Have you checked out Android’s multi-window feature yet? It can make it a lot easier to switch back and forth between open apps.
First, open Settings on your phone.
Then choose Display.
Then check Multi-Window. (You can also swipe down from the top of your home screen with two fingers and select Multi-Window from the Quick Settings Menu.)
Depending on the phone you may have a little arrow on the side of the screen or you may need to press and your back button to see this sidebar menu.
Just press and hold the app you want to share the screen and drag it out onto the home screen.
The app will open. Then select the second app and pull it out onto the home screen. You can also do this by pressing and holding your home icon or button to see all of your open apps.
You’ll notice some of the apps have a little multi-window icon on the right side next to the X. Just tap that to select apps to view in multi-screen.
This is what the multi-screen view looks like. I could browse photos while keeping a messaging app open. Or watch a video while I read email.
Press and drag the little dot at the border between the apps to resize the windows.