How to download partial document data in Android Cloud Firestore?

Question

I have my database on Cloud Firestore. The data is read-only. And the client application is an Android App written in Kotlin.

My database is something like this:

collection{courses}
    document{doc1}
        name: "csn206"
        ...
        ...
    document{doc2}
        name: "csn207"
        ...
        ...
    document{doc3}
        name: "csn301"
        ...
        ...    

I am trying to access my data in this way:

val db = FirebaseFirestore.getInstance().collection("courses")
db
    .get()
    .addOnCompleteListener{
        // display list of documents
    }

But, this downloads everything. I want reduce the unnecessary usage of Internet.

So, what I want to do is display name values of all documents in a list. And select the documents which are needed to be downloaded completely.

So, my question is how to get list of all documents' name values, without getting all of the documents?