Huawei G6 - I Cannot Install an Application, Why, and How Do I Solve the Problem

Uninstallation:
Touch Settings > Manage apps. Touch the application you want to uninstall and then touch
Uninstall > OK.
2.11.5 I cannot install an application, why, and how do I solve the
problem?

Possible causes are as follows:
The Android application package (APK) is corrupted. To solve this problem, contact the
APK provider.

The application has already been installed. To solve this problem, uninstall and reinstall
the application.