Seeing Dortmund succeed in beating Real Madrid was indeed a very surprising thing and at the same time gave us an idea that the impossible can still be won even for the team that is not the favorite. I think everyone knows that beating Real Madrid is impossible, but as long as they don't try and try to beat all the available statistics then they won't know that there is always a miracle waiting.
Real Madrid does not have an unbeaten season so far and beating them is actually impossible.
If other clubs can beat Real Madrid, Dortmund can beat Real Madrid too, even in the Champions League final match. Many years ago, who thought Dortmund will beat Juventus in a Champions League final match but they did it and won a first Champions League title for their club.
Now they will have another chance to win a second Champions League title for their club, after losing another final match some seasons ago against Bayern Munich. Dortmund have less experience than Real Madrid in Champions League final match and most of their current players nearly don't have this experience. It will be advantage of Real Madrid and disadvantage of Dortmund but it's scarce opportunity to win a big title so Dortmund players will play and fight as best as possible to win it.