You cannot use Spotify offline with the Galaxy Fit3 (40 mm) as the watch does not have its own music storage or Spotify app. However, you can control music playback on your smartphone (e.g. play/pause, skip tracks, volume) directly from the watch as long as your mobile is within range. For true offline listening with Bluetooth headphones without a mobile phone, you need a model with integrated music storage and Spotify app, which is not the case with the Galaxy Fit3.