Kotlin and Firestore database, query by name error

 fun loadFirestoreDatas() {
    progress1.visibility = View.VISIBLE

    val memberCollection = db.collection("Radiolgy")

    var query: Query
            = memberCollection.orderBy("name").startAt(tt.text).endAt("\uf8ff" + tt.text)


    /*  if (searh.text.toString().length > 0) {



        //query = memberCollection.whereEqualTo("name", searh.text.toString())

       query =  memberCollection.orderBy("name").startAt(searh.text).endAt("\uf8ff" + searh.text)

    }*/

    query.get()
            .addOnCompleteListener { task ->
                if (task.isSuccessful) {
                    emloyeelist.clear()
                    for (document in task.result) {
                        var cur_data: CENTER_data = document.toObject(CENTER_data::class.java)
                        cur_data.id = document.id
                        emloyeelist.add(cur_data)

                    }
                    val adapter = Employee_Adapter(this@RADIOLGY, R.layout.tict_center, emloyeelist)
                    listview.adapter = adapter
                    progress1.visibility = View.GONE
                } else {
                    Log.d(ContentValues.TAG, "Error getting documents: ", task.exception)
                }
            }

I want guery by name, but I don't know what the error is in this code.