It is one of the most common problem in android operating system. Usually when you open an app, you will see a black screen for few seconds and then app will crash with or without an error message. There are few ways to fix this problem. Most of the times, it might be a temporary loading issue. You just need to press the recent applications menu (usually the first left button) in your phone. Then you close the app that has this issue. Now open the app again. It may work normally. Try Hard reboot in your Android mobile. Press and hold down the "Home" and "Power" buttons at the same time for upto 10 seconds. Then, release the buttons and hold down "Power" button until the screen turns on.Now you can try opening the app, it may work fine. If none of the above working, you can wait till your phone battery drains and it turns off automatically. After that put it to charge, and press the power button. It may work after this. Finally, if you can't fix it with anything, you may need to uninstall the app and re-install it. Android usually restores all settings after you re-install and log into the app. You can see if that fixes it. Even in some rare cases, the re-install step also don't work. If that is your case, try installing older versions of the app. Good luck!