Not get points yet in last two Champion League matches will make Union Berlin have difficult chance if want qualify to next round, I think in Group C Madrid and Napoli will qualify to knock out round.
Union Berlin are at their weakest moments whether in 1.Bundesliga or in Champions League. They are just above the relegation zone with only two victories and 4 defeats. Here in UEFA Champions League, they didn't win a single match and I don't expect them to do with Napoli. Best they can do is to pick the third place to Europa League group stage and try their chance there although I doubt they could go far in any competition this season..