Sometimes simply deleting the app from your Android device is not enough... files and data can be left over which keeps you from working from a clean slate!
Fortunately, removing these lurking files is pretty simple:
Go to Settings
Open Apps
Select the app to uninstall
Press Force Stop
Press Storage
Press Clear Cache
Press Clear Data
Return to the app screen
Press Uninstall
That should get rid of most of the files, folders and caches created by the app and then remove the app itself!