Follow these instructions step by step:
1. Charge up your iPhone:
Connect your iPhone with your computer or with the power supply.
2. Close the current program:
Hold down the standby button on the top of the iPhone for a few seconds until a red slider is displayed. Press and hold down the round Home button until the program currently in use is terminated.
3. Switch off the iPhone completely:
If the previous steps do not work, switch the iPhone off completely and then switch it on again. Hold down the standby button on the top of the iPhone for a few seconds until a red slider appears and move your finger over the slider control. Then press and hold down the standby button until the Apple logo appears.
4. Reset the iPhone:
If your iPhone still is not working, reset it. To do this, press the standby and the Home button simultaneously for at least ten seconds until the Apple logo appears.
5. Reset the iPhone settings (software reset):
If your iPhone still is not working, you need to reset the iPhone settings. Go to "Settings" > "General" > "Reset" > "All settings". All your settings will be reset. This will not delete your data and media.