Hertha Berlin are stuck in the Bundesliga’s automatic relegation places after being outwitted 4-1 by visitors Union Berlin in the city derby on Saturday. Grischa Prömel scored the key goal for 2-1 as seventh-placed Union racked up a third win over their rivals this term. Bundesliga leaders Bayern Munich earlier needed a Robert Lewandowski penalty eights minutes from time to seal a 1-0 home win over Augsburg on and move closer to their 10th straight title. Second-placed Borussia Dortmund had won 2-0 at struggling Stuttgart on Friday and Bayern’s fortunate win means the gap is nine points with j…