Android : Android saving file to device and can't open it

so, I'm trying to open a file I save to my device, but the file say that I can't open the file. the device tells me : "This document cannot be opened".

here's my code, the file is .ppt format. thanks a lot !

obviously i have those permissions in the manifest:

    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

here's the code:

String fileName = doc.getName();

                String packageName = fragment.getActivity().getPackageName();
                String path = Environment.getExternalStorageDirectory().getAbsolutePath()+ "/Android/data/" + packageName + "/files/";

                File saveFile = new File(path + fileName);

                File parentDest = saveFile.getParentFile();
                if (!parentDest.exists()) {
                    parentDest.mkdirs(); //make all the directory structures needed
                }
                if (!saveFile.exists()) {

                    try {
                        saveFile.createNewFile();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }

                    Toast.makeText(getContext(), "Downloading...", Toast.LENGTH_SHORT).show();

                    downloadingDocs.add(doc);

                    final DownloadManager downloadManager;

                    final long myDownloadReference;

                    downloadManager = (DownloadManager) fragment.getActivity().getSystemService(Context.DOWNLOAD_SERVICE);

                    Uri uri = Uri.parse(url);

                    DownloadManager.Request request = new DownloadManager.Request(uri);

                    request.addRequestHeader("Authorization", "Basic " + SharedPref.getAuthPrefValue());
                    request.addRequestHeader("Device", BaseApplication.getCurrentDevice().getDevice().toString());
                    request.addRequestHeader("DeviceId", BaseApplication.getCurrentDevice().getDeviceId());
                    request.setDescription(fileName).setTitle("Downloading Document");
                    request.setDestinationInExternalFilesDir(getContext(), path, fileName);
                    request.setVisibleInDownloadsUi(true);
                    request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI | DownloadManager.Request.NETWORK_MOBILE);

                    myDownloadReference = downloadManager.enqueue(request);

                    finalHolder1.downloadProgress.setVisibility(View.VISIBLE);

                    new Thread(new Runnable() {
                        @Override
                        public void run() {

                            downloading = true;

                            while (downloading) {

                                DownloadManager.Query q = new DownloadManager.Query();
                                q.setFilterById(myDownloadReference);

                                Cursor cursor = downloadManager.query(q);
                                cursor.moveToFirst();
                                int bytes_downloaded = cursor.getInt(cursor
                                        .getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
                                int bytes_total = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));

                                if (cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS)) == DownloadManager.STATUS_SUCCESSFUL) {
                                    downloading = false;
                                    downloadingDocs.remove(doc);
                                }
                                //final double dl_progress = (bytes_downloaded / bytes_total) * 100;
                                final int dl_progress = (int) ((bytes_downloaded * 100l) / bytes_total);

                                fragment.getActivity().runOnUiThread(new Runnable() {

                                    @Override
                                    public void run() {
                                        finalHolder2.downloadProgress.setProgress((int) dl_progress);
                                    }
                                });
                                cursor.close();
                            }
                        }
                    }).start();



                } else {

                    Intent intent = new Intent();
                    intent.setAction(android.content.Intent.ACTION_VIEW);
                    intent.setDataAndType(Uri.fromFile(saveFile), "application/vnd.ms-powerpoint");

                    fragment.getActivity().startActivity(intent);
                }