Sign in to your Google Account
Go to myaccount.google.com
Open Data & privacy
Scroll to Data from apps and services you use
Select Delete a Google service
Sign in again if prompted
Find Gmail and click the delete icon
Enter an email address that is not Gmail to use for other Google services
Verify the non-Gmail email address
Follow the prompts to confirm deletion
Review the warning about losing Gmail data
Confirm the deletion of Gmail
Save any important emails before deleting
Update any accounts that use your Gmail address before closing it