Hello Hachi,
Welcome to the QuickBooks family! Noting open invoices in QuickBooks Desktop, can be rather concerning. I would be glad to provide some insight here!
Although you can record invoice payments, so they're marked as paid, rather than overdue, these changes can have a negative impact on your books. For this reason, it's best to speak with an accounting professional for their expertise and best course of action. If you don't have an accountant, we can help you locate a ProAdvisor in your local area.
Feel free to reach out again, if you have other questions. We'd be happy to help!