Reset Network Settings:

NOTE: By resetting your network settings, all your saved Wi-Fi and Bluetooth networks will be removed. Furthermore, data restrictive settings, background sync settings, and network selection mode will be restored to factory values.

  1. Open “Settings
  2. Access “General management
  3. Tap “Reset” > “Reset network settings
  4. If your phone is protected by a lock screen, enter your PIN/password to proceed
  5. Tap “Reset settings

Factory Reset

WARNING! When you factory reset your phone, all your personal data located on the device’s internal memory will be deleted, including apps, media files, contacts, downloaded content etc. Data located on the SIM and SD cards won’t be affected.

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

Hard Reset via Settings:

  1. Open “Settings
  2. Access “Cloud and accounts
  3. Tap “Backup and restore” and optionally, enable or disable “Back up my data” and “restore
  4. Return to “Settings” and access “General management
  5. Tap “Reset” > “Factory data reset
  6. Tap “Reset device
  7. If your device is protected by a lock screen, enter your password/PIN and tap “Continue
  8. When ready, tap “Delete all

Hard Reset via Android Recovery:

NOTE: If your device crashes, freezes, or otherwise it prevents you from resetting it via Settings, alternatively you can try resetting your device from the Android Recovery menu.

  1. Turn the phone off
  2. Next press and hold “Home” and “Volume Up” at the same time, then press and release “Power
  3. At the Android screen, release the buttons and wait for access to Recovery
  4. Once in Recovery, press “Volume down” to navigate the menu and highlight “Wipe data/factory reset
  5. Press “Power” to select the highlighted option
  6. Highlight “Yes – delete all user data” and press “Power
  7. After the process completes, highlight “Reboot system now” and press “Power” one last time to confirm

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