As per my project requirement, I want to download files from the chosen directory via API. I can list all the files/subfolders from the chosen directory but I didn't find any way to download any files from the chosen directory and sub-directory using API.
If you received a shared link for a folder from the Dropbox Chooser, which would look like "https://www.dropbox.com/sh/...", you can then list the contents of that shared link using the Dropbox API, via the /2/files/list_folder[/continue] endpoints. You should supply the shared link as the "shared_link" parameter, and use the empty string "" as the value for the "path" parameter to list the contents of the root of the linked folder. (You can repeat with paths relative to that folder root to get nested folders, if desired.)
From there, once you know the paths of the contents, based on the result of the above call(s), you can then download the file(s).