Granular: Permission & Share to Public

I would like to have granular permissions to access every document and folder, similar to Notion, including the option to share with the public. I was a bit shocked to find that I had granted only one permission to one of my employees, but to my surprise, he received access to all of my folders across the workspace.

My expectation is that each folder should belong to one of my clients, with full access granted specifically to them, while each folder should have limited access for my staff. Not all of my staff should have access to all clients to maintain privacy and data confidentiality.