Good afternoon Lily.
Here is a video material on all updates regarding files:
https://www.youtube.com/watch?v=y5ydgFtsDjsRegarding your questions:
1. Access to files is configured through the contact's access rights.
Through access rights, you can configure:
- Access to all folders and files.
- Access to folders and files that do not have an author, for example, files when imported from letters or audio recordings of telephony conversations.
- Access to folders and files of a certain employee.
- Access to folders and files that you created directly.
2. File preview can be implemented through standard mechanisms, or by viewing a Google Docs document (mainly xls/xlsx files).
Also, document preview can be configured directly in the browser.
3. Unfortunately, there is no such possibility, you can only give access to all folders / files of a certain employee. You cannot give permission to a specific file or folder.