The next game for Newcastle will be key. If they win their home game against Dortmund, I would say that they have amost made it through the group stage unless they lose all of their last 3 games. I know there is still some speculation involved because the group is so close, but the team that has a head start in this close group is probably one of the teams that comes out successful. They have the goal advantage against PSG or they would have to get slaughtered. They have a home game against AC Milan and did not concede a goal there. They are in a great position to master the hardest group of this Champions League season.
Newcastle United are unbeatable after two matches in their group and you are right, a next match with Dortmund will be a key for them to open a gate to the next round. If they win over Dortmund at their home stadium, they will secure their first position in this group and a second half of this group will be less pressure for them.
Dortmund are not weak as they shown that they managed to get a draw with AC Milan just like how Newcastle United did. The match between Newcastle United and Dortmund will be very balancing in theory but with a home stadium advantage and fan support as well as current good mentality, Newcastle United do have chance to win. The challenge for them does not come from Dortmund but come from themselves. After beating PSG with a big result, will they keep calm to host Dortmund?
This is a big issue for their coach and players because if they play carelessly, Dortmund are good enough to exploit Newcastle United's careless and even can take three points to go home. This group is very tightly and Newcastle United must be very careful in a next match.