Hard Reset SAMSUNG A300F Galaxy A3

First method:

1. At the very beginning hold down the Power key to switch off your phone.
2. Now press and hold together: Volume Up + Home  + Power button, until you see Samsung logo.
3. Release held keys when Recovery Mode appears on the screen.
4. Then select from menu "wipe data / factory reset" using Volume buttons to navigate andPower button to confirm.
5. Next choose "Yes -- delete all user data" to confirm whole operation.
6. After that select option "reboot system now".
7. Well done!

Second method:

1. Check that your phone is on.
2. From the Main Menu find and select Settings.
3. Tap Backup&Reset and then Factory Data Reset.
4. Afterwards choose Reset device.
5. To confirm your choice select Erase everything.
6. That's all.

WARNING !
Hard Reset will erase all of your data
All described operations you are doing at your own risk.