var auth = new Authorization("[email protected]", "p@ssword");
await auth.Login();

using (var downloader = new Downloader(auth))
using (var stream = await downloader.OpenFile("FortniteGame/Content/Movies/Onboarding_Appended_Intro.mp4"))
using (var outStream = File.OpenWrite("out.mp4"))
    await stream.CopyToAsync(outStream);

using (var downloader = new Downloader(auth))
using (var stream = await downloader.OpenFile("FortniteGame/Content/Movies/Onboarding_Appended_Intro.mp4"))
using (var outStream = File.OpenWrite("out.mp4"))
{
    double progress = 0;
    byte[] buffer = new byte[1024 * 1024]; // 1 MB
    int read;
    while ((read = await stream.ReadAsync(buffer, 0, buffer.Length).ConfigureAwait(false)) > 0)
    {
        await outStream.WriteAsync(buffer, 0, read).ConfigureAwait(false);

        // report progress back
        progress += (double)read / stream.Length * 100;
        Console.Write($"\r{new string('=', (int)progress / 2)}{new string('-', (int)(100 - progress) / 2)} {Math.Round(progress, 2)}%");
    }
}