Back up your data (Samsung Cloud, Google account, or Smart Switch)
Charge your phone to at least 50%
Go to Settings > General management > Reset
Tap Factory data reset
Tap Reset
Enter your PIN/pattern/password if prompted
Tap Delete all
If prompted, confirm your Samsung account password
Wait for the reset to complete and the phone to restart
If you can’t access the Settings menu, power off the phone
Press and hold Volume Up and Power (or Bixby + Volume Up + Power on some models)
Release buttons when the Android Recovery screen appears
Use Volume buttons to highlight Wipe data/factory reset
Press Power to select
Highlight Yes and press Power to confirm
Select Reboot system now and press Power