1st Step : Sign in to your Google Account.
2nd Step : Once signed in, click on the Security tab.
3rd Step : scroll down to “Your Devices”. Click on “Manage Devices”.
4th Step : Click the 3-dot dropdown on the device you wish to remove from your account, then click “Sign Out”.
5th Step : There will be a confirmation window, select “Sign Out”.
6th Step : A confirmation window will show that the access has been removed from your device.
7th Step : To confirm, you can review the “Where you’ve signed out” list. The selected phone will show here.
Please Note : You need to do your own research to protect your information and data also make you gadget / device ready to sale or donation .