Hello, -avremax-com.
Thank you for reaching out to the Community. To back up and restore the file in QuickBooks Online isn't available. You have to convert your data to QB Desktop files (i.e QBW) or export them all out to XLS/CSV files.
You can check this article as a reference on how to Import and export data in QuickBooks Desktop.
Additionally, to learn more about the list and report you can export to QBO, please check out this article: Export reports, lists, and other data from QuickBooks Online.
Please let me know if you have other concerns. I'll be here to lend a hand. Stay safe!