Synchronize contacts with remote database

I try to synchronize the contacts of the mobile device with a database in this case Postgresql, the way I do it does not seem to be the most convenient.

    public void sincronizarcontactos(){

    // Se tiene permiso
    final String[] projeccion = new String[]{ContactsContract.CommonDataKinds.Phone._ID,ContactsContract.Data.DISPLAY_NAME, ContactsContract.CommonDataKinds.Phone.NUMBER, ContactsContract.CommonDataKinds.Phone.NORMALIZED_NUMBER};
    String selectionClause = ContactsContract.Data.MIMETYPE + "='" +
            ContactsContract.CommonDataKinds.Phone.CONTENT_ITEM_TYPE + "' AND "
            + ContactsContract.CommonDataKinds.Phone.NUMBER + " IS NOT NULL";
    String sortOrder = ContactsContract.Data.DISPLAY_NAME + " ASC";

    final Cursor c = getContentResolver().query(
            ContactsContract.Data.CONTENT_URI,
            projeccion,
            selectionClause,
            null,
            sortOrder);

    HashSet<String> normalizedNumbersAlreadyFound = new HashSet<>();
    int indexOfNormalizedNumber = c.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NORMALIZED_NUMBER);
    progreso= ProgressDialog.show(SincronizarActivity.this, "", "Sincronizando...", true);

    int o=0;

    while(c.moveToNext()){
        o++;
        progreso.show();
        String email=c.getString(0).replace(" ","_");
        String normalizedNumber = c.getString(indexOfNormalizedNumber);
        if(normalizedNumbersAlreadyFound.add(normalizedNumber)){
            String urlinsert="http://192.168.1.33/Agenda/insert_persona.php?name="+c.getString(0)+
                    "&city=Paute&email="+email+"@gmail.com&phone="+c.getString(1)+"&mobile="+c.getString(2);

            JsonObjectRequest solicitud = new JsonObjectRequest(urlinsert,null, new Response.Listener<JSONObject>(){
                @Override
                public void onResponse(JSONObject datos) {
                    Toast.makeText(SincronizarActivity.this, "Guardado", Toast.LENGTH_SHORT).show();
                }
            },new Response.ErrorListener(){
                @Override
                public void onErrorResponse(VolleyError error) {
                    progreso.dismiss();
                    Toast.makeText(SincronizarActivity.this, "Tuvimos un problema de conexión...", Toast.LENGTH_SHORT).show();
                }
            });
            VolleyRP.addToQueue(solicitud,request,this,volley);
        }

        if (o==projeccion.length){
            progreso.dismiss();
        }

    }
    progreso.dismiss();
    Toast.makeText(SincronizarActivity.this, "Se han sicronizado sus contactos...", Toast.LENGTH_SHORT).show();
    c.close();
}

As I say, it does not seem to me to be the most correct way, I would like you to help me to get them to synchronize automatically, as in the photo ...

I hope you can help me with this ...