If you want your Android phone to automatically fit itself to the size of whatever screen it's being displayed on, there are a few things you can do. First, make sure that your phone's display is set to automatic in the Display settings. Then, go into the Google Play Store and download an app called Auto Fit Wallpaper. Once you've installed this app, open it and select the Set as Wallpaper option. Your phone will now automatically adjust its resolution and wallpaper size based on the screen it's being displayed on.