You can delete your all unwanted Emails on Gmail by cleaning up. You can delete it by picking unwanted mails first. Go on search option which is on the top. Here you can search the mail which you want to delete. Now select the mails and you will see a delete icon option at the top line. Delete it from Gmail.
You can delete mails by opening it and clicking on three dots menu. You will see an option of delete there.
You can delete your mails directly from label as well. Go to your label and remove it from your Gmail. You can make a label of all unwanted mails and can delete the label.
You can select the particular user in search tab and delete it’s all mails.