If you are unable to delete a project, it means you might not have the necessary rights. To change that, a manager needs to edit your permissions within Company Settings, following the steps below.
Step 1: In Company Settings, under Team or External users, they can see what role each user has.
Step 2: After locating the user that needs to be edited, they have the option to click on the three-dotted icon on the right-hand side, or select the checkbox on the left and edit in bulk, if necessary, and change the current role to one that includes the permission to delete projects.
In case a new role needs to be created, please refer them to this article.