Bayer Leverkusen are close to a domestic double in the Bundesliga and German Cup but coach Xabi Alonso has warned that nothing is decided yet as he recalled the ghosts of the past. Unbeaten in all their 40 season matches, Leverkusen visit Union Berlin on Saturday with a 13-point Bundesliga lead. They return to Berlin for the May 25 Cup final where they are big favourites against second division Kaiserslautern. Leverkusen are also in the Europa League quarter-finals and Alonso told reporters on Friday that “the situation is very good at the moment. We can achieve big goals in all competitions. …