You do NOT have to order everything in your cart. On the checkout page, the check boxes will allow you to select or de-select the items that you wish to pay for.
You can select ALL the orders, or just one of them.
You can view a 1 minute tutorial how here:
That is how you will remove them from your cart:
If you want to PERMANENTLY delete an unpaid order from your account, you may do so by clicking on “Delete Order” at the bottom right of the Proof Order Page (with the photo and background option)
Here is a 1 minute tutorial here: