Retrieve File Index issue

I am trying to retrieve file information from HighQ for only active sites. Upon investigating, I found that there are 206 active sites on HighQ and but when executing the API to fetch files

, I only received 3,217 files spanning about 5 distinct site IDs. The business informed me that there are around 33000 documents that are present on HighQ. I am currently using this endpoint for the

API call to get Site information : https://collaborate.ocorian.com/estera/api/1/sites?filterby=all.

For root SiteFolder:"">collaborate.ocorian.com/.../" + si.sitefolderID + "/items"

Gets the items inside folder: "">collaborate.ocorian.com/.../" + fol.id.ToString() + "/items";

Get files : "collaborate.ocorian.com/.../files + fol.id.ToString() + "\"";

This is a small sample of how the file info is being saved:

 

What is the best approach to retrieve all file details (file info only) from HighQ?