Borussia Dortmund striker Sebastien Haller’s surgery for a testicular tumour went “very well” and he could be back playing in a few months, sporting director Sebastian Kehl has said. The new buy from Ajax was diagnosed just days after his medical when signing. The 28-year-old former Eintracht Frankfurt player was bought as a replacement for Erling Haaland, who left for Manchester City. “The operation went very, very well and he is on a very good path,” Kehl said in a video interview with Dortmund’s shirt sponsor 1&1. “He was…incredibly positive and also told the team: ‘Do your job, give ever…