Reset Network Settings:

NOTE: Resetting network settings will delete connection data such as Wi-Fi and Bluetooth networks. Background data sync, network selection mode, and data restrictive setting will be switched to default values.

  1. Open “General Manager
  2. Tap “Reset” > “Reset network settings
  3. Tap “reset settings
  4. Enter your PIN and tap “Reset settings” to confirm

Soft Reset via Hardware Keys:

NOTE: A soft reset is designed to simulate battery removal and this can be useful if the devie becomes unresponsive. A soft reset will not delete any personal data stored on the phone.

  1. Press and hold “Power” and “Volume down” for up to 45 seconds
  2. Wait for the phone to finish rebooting

Hard Reset

NOTE: When you hard/factory reset your phone, all personal data on the phone will be deleted. This includes downloaded content, ringtones, apps, contacts etc. Furthermore all settings will be restored to factory values.

Before you reset the phone you can check this thread for a guide on how to back up data, and this guide for restoring data.

Hard Reset via Settings:

  1. Open the apps drawer
  2. Launch “Settings” > “Cloud and accounts
  3. Tap “Backup and restore
  4. Optionally, turn “Back up my data” and “Restore” ON or OFF
  5. Return to “Settings” and access “General Management
  6. Tap “Reset” > “Factory data reset
  7. Tap “Reset device
  8. If necessary, enter your PIN or password to proceed
  9. When ready, tap “Continue” > “Delete all

Hard Reset via Recovery:

NOTE: If you are unable to reset the phone using the method above, alternatively you can try resetting the device via Android Recovery using hardware buttons.

  1. First turn the phone off
  2. Next, press and hold “Volume Up” and “Home” at the same time, then press and hold “Power” as well
  3. At the “Android” logo, release all the keys and wait for access to Recovery
  4. Once in Android Recovery, press “Volume down” repeatedly to navigate to and highlight “wipe data/factory reset
  5. Press “Power” to select the highlighted option
  6. Press “Volume down” repeatedly to highlight “Yes – delete all user data
  7. Press “Power
  8. Once the reset is done, ensure “Reboot system now” and press “Power” one last time

See More: Samsung Galaxy A8 (2018): Soft/Hard Reset via Settings or Recovery