When deleting a project, it is sent to the recycle bin. Projects are deleted from the project creation panel ( in the "Catalogue" section). Author users have access to this panel.
Do not forget to empty the Recycle Bin often to avoid taking up too much storage space.
As Administrator you can recover a project or delete it definetely.
Go to "Administration" >> "Recycle bin".
From the "Options" column, we can: