WordPress itself does not have a “delete website” button. If you want to delete the entire website, you must do so via the access provided by your host and delete both the directories and files as well as the database. If you need assistance with this, please contact your host’s support team.
However, if you only want to delete your own access to WordPress, someone else with administrative privileges in your project will have to do this for you. They will need to find your account under Users and click on Delete. You cannot do this yourself. The website will remain available as normal, but you will lose access to the backend of the website.
Please make sure you create a backup before doing anything.