How to specifically retrieve data from firebase and show it on the listview? [on hold]

Here is the coding for my listview. I want to extract the data specifically from the database and show it into the listview. I am querying the data based on position of the player. Eg: if user enters "goalkeeper", all data of the players that are goalkeeper will be retrieved and show on the listview including name, club, nationality. The second image is my firebase data structure. Thanks you in advance from me.