This problem happens a lot and, although it is very annoying, it is not so difficult to solve. Although it should not be something common, the truth is that applications sometimes present this problem that may be related to errors in the application or perhaps your operating system is not the best or newest for such applications. There are apps that are constantly adding new options and improving some details for better performance, but sometimes your phone just can't support the latest version and the app starts to stop all the time.
The solution
The first thing you should try is to restart your phone and start using the application again. You can also go to the Application Manager and stop the application, sometimes cleaning the data from the cache also works. If you continue to do the same, try uninstalling the application and installing it again. As mentioned above, applications sometimes contain many errors that cause this problem.