Barcelona and Germany goalkeeper Marc-André ter Stegen will undergo an operation to treat back problems that have sidelined him lately. Barcelona said that Ter Stegen “will undergo a surgical procedure this week to address the lower back issues he is experiencing.” It was not clear immediately the 31-year-old will be out of action, with Barca saying only a new statement would come after the operation. Ter Stegen missed Germany’s two November friendlies and the following three Barca games with the nagging issue. He said on X, formerly Twitter, the the decision to go under the knife came “after …