When using safe mode on your handset, only the basic system software will be accessible.
Here's how to switch to and use Safe mode on your Samsung Galaxy S5:
1. Turn your phone OFF.
2. Press and hold the Power/Lock key for about one to two seconds. Doing so will power device ON.
3. Wait until the Samsung logo appears.
4. Now press and hold the Volume down key until you see the lock screen.
5. When the lock screen displays, you can see "Safe mode" in the lower-left corner of the screen.
6. Now swipe the screen in any direction. Doing so will unlock the device screen.
You can use the Application Manager located in your phone Settings to uninstall third-party apps or app updates, if your device is working properly in Safe mode.
7. Once your done troubleshooting certain device issues in Safe mode, restart your device by pressing and holding the Power/Lock key. Doing so will likewise exit Safe Mode.
8. Touch Restart to initiate phone restart.
If necessary, restart your device by removing and re-inserting the battery, then pressing and holding the Power/Lock key.