Sign in to your Google Account
Go to your Google Account settings
Open the Data & privacy section
Scroll to the section for data from apps and services you use
Select Download your data if you want to save a copy
Go to More options or the Delete your Google Account / Delete a Google service section
Select Delete a Google service
Sign in again if prompted
Find Gmail in the list of services
Click the delete icon next to Gmail
Enter an alternate email address that is not a Gmail address
Verify the alternate email address
Open the confirmation email sent to the alternate address
Follow the confirmation link
Confirm the permanent deletion of Gmail
Remove Gmail from any accounts or services that use it as a login email
Update recovery email addresses and contact information on other accounts
Check that you no longer need Gmail before completing deletion