How does Samsung S5 adjust the encryption method?

According to your description, if your mobile phone is encrypted, you can't change the lock screen mode. If you need to change, you should decrypt the phone securely. Please go out of the mobile phone application-Settings-More-Security. After entering, the security check requires decryption of the equipment. Or you can restore the mobile phone to the factory settings, and pay attention to backing up the mobile phone data first.