To easily backup SharePoint Online site the best thing is to use a SharePoint Backup Tool. So, if I had to recommend one then the Shoviv SharePoint Backup Tool is the best option. This utility offers a robust and user-friendly solution for backing up SharePoint Online site. 

Its comprehensive features, ease of use, and reliability make it an ideal choice for businesses looking to protect their SharePoint environments. By integrating this tool into your backup strategy, you can ensure the safety and integrity of your critical data, providing peace of mind and enhancing your overall data protection framework.