The very first thing you need to do if you want to make a switch from an old Android smartphone to a new one is adding your Google account. Without a Google account, you won’t be able to install apps from the Play Store. On the Android system, a Google account is used to use Google’s services and apps installed on your smartphone. In addition to Play Store, you need your Google account to use Gmail, Google Maps, and other apps from Google.
Quick question. How to remove the Google account you have added on your old Android device? You can do so from the Settings menu.
Note: This article specifically covers the Samsung Galaxy device running on Android 8.0 with Samsung Experience 9.0
To remove your Google account from an Android smartphone, go to the Settings menu by tapping the gear icon. Under this menu, you will see a Cloud and account options. Tap on it.

On the next screen, tap the Accounts option and select the Google account you want to remove and tap the REMOVE ACCOUNT button.

If you want to replace your old smartphone, make sure to remove the Google account you use on the Play Store (if you added more than one Google accounts). You can go to the same screen (CLOUD AND ACCOUNTS) every time you want to remove an account from the services you added on your device.