The best way to prevent anyone from obtaining unauthorized access to your Gmail account is to turn on 2-step verification.
Sign into your Gmail account.
Click on the gear icon on the top right of the screen.
Click on mail settings.
Click on accounts and import at the top of this menu.
Click on other Google account settings.
Click on using 2-step verification.
You will be asked for your password at this step.
Now you will add your mobile or landline phone number.
Now you choose whether to receive the code by text message or a phone call.
Send codes by:
SMS text message
Voice call
Next, enter the code you receive by text message or phone call in the box provided.
Click on “the remember this computer for 30 days” box, so you will only have to receive phone verification codes once a month.
If you use 2-step verification, hackers who steal your password will not be able to log into your Gmail account because they won’t be able to answer your phone to get the verification code Google will call to give you whenever you try to log into your Gmail from a different computer.