Create SharePoint online document library, create folders and manage access.
Some useful info: What is a document library?
A document library provides a secure place to store files where you and your co-workers can find them easily, work on them together, and access them from any device at any time. For example, you can use a document library on a site in SharePoint to store all files related to a specific project or a specific client. Adding files or moving files between folders is as easy as dragging and dropping them from one location to another.