How do I safely take out my Gdrive after my laptop has been backed up?

For information about ejecting an external drive, see the following from: Connect and use other storage devices with Mac - Apple Support

Eject a storage device

On your Mac, do one of the following:

• Select the item to eject, then choose File > Eject.

• In the Finder sidebar, click the Eject button  next to the item’s name.

• Tip: You can quickly eject disks from connected optical drives using the Eject menu in the menu bar. Choose Apple menu  > System Settings, then click CDs & DVDs  in the sidebar (you may need to scroll down). Turn on “Show eject in menu bar.” 

Note: If you don’t have an optical drive connected to your Mac, CDs & DVDs settings aren’t available.

• On the desktop, drag the item that you want to eject to the Trash.

If you can’t eject a storage device, another app or user may be using one or more files on the storage device. See If you can’t eject a disk on Mac because an app is using it and If you can’t eject a disk because another user is using it.