Samsung Galaxy A8 Duos delete your Google & Gmail account

OS: Android 5.1 (Lollipop), upgradable to 6.0 (Marshmallow)

CPU: Octa-core (4x1.8 GHz Cortex-A53 & 4x1.3 GHz Cortex-A53) - A800Y
Octa-core (4x1.8 GHz Cortex-A15 & 4x1.3 GHz Cortex-A7) - A800F

Display: 5.7 inches, 89.6 cm²

Battery: Non-removable Li-Ion 3050 mAh battery

Remove a Google account on Samsung Galaxy A8 Duos

If you are going to sell your old phone, you definitely need to delete your google account from your phone so that the new user cannot access your google profile and cause problems with google services.

What happens after deleting a Google account?
Emails, all data and content, including files and photos, will be deleted.
You won't be able to use Google services that require an account (such as Gmail, Drive, Calendar, or Google Play).
You will lose access to subscriptions and content purchased through this account on YouTube and Google Play (for example, applications, games, music, TV series).

How do I remove a Google account from my phone?
Go to Settings on your phone.
After that, select the menu item Accounts and backup.
Select Manage accounts and delete your account.