Nicolene,
You will need to set 11.7 Approval Flow to 'Auto-submit and approve' so that the Reopen button will not show in the Toolbar. The Delete button will remain as, in theory, the user should be allowed to control their time. After all, you are not even using the approval process, so this is left open.
If you want to block the ability to delete time, then you will need to create a Validation Rule that blocks this. At the same time, understand that if a user enters time incorrectly and needs to change it, they will not be able to and will require the help of a Project Manager or Admin/Superuser that is not being blocked by the Validation Rule.
Sincerely,
Boris Krutiy - Clarizen Success