My file sharing settings are completely ignored

I want to configure file sharing from my Macbook Pro running Monterey so that my home folder has read and write access to me and no access to anyone else. And I would like the same for an external SSD. However, no matter what I do in the Sharing preferences, such as entering the names of specific subfolders that I would like to share and assigning myself read and write access, and no matter what I do when I click on Sharing in Get Info in Finder, including propagating the permissions down through the whole directory tree, I cannot actually change the permissions. I can make the external SSD visible to Windows Explorer and to the file sharing app on my Samsung phone, but I don't have permission to enter it. And I can see all the top-level contents of my home folder, but if I look in any of its subfolders except Public on the Android phone, I see nothing, and in Windows, when I click on any of these folders, I am told that I don't have permission to look at it.

I also have the issue that the Mac doesn't appear in the network browser in Windows Explorer, which means that I need to enter the Mac's device name in the address bar, although it is visible from the Android phone. This is a minor annoyance compared to the inability to access the folders and volume concerned at all.

How do I get file sharing to behave sanely?