Open Gmail in a web browser
Sign in to your account
Use the search bar to find the emails you want to delete
Click the checkbox at the top left to select all visible emails
Click the message that appears to select all conversations matching the search
Click the Delete icon
Empty the Trash if you want to remove them permanently
To delete all emails in a label, open the label and repeat the same steps
To delete emails from a sender, search by sender name or email address and delete the results
To delete old emails, search by date or use search operators like older_than:30d
To delete unread emails, search is:unread and delete the results