Robert Lewandowski started pre-season training at Bayern Munich on Wednesday amid a report that Barcelona believe they can sign the World Footballer of the Year before the end of the week. Lewandowski, 33, had his first training unit the day after undergoing fitness tests in Munich. However, Lewandowski has made it clear in the off-season that he wants to leave Munich after eight years in summer despite a contract until 2023. Bayern bosses have so far said they won’t let him go. But they are reportedly ready to listen to offers of €50 million ($50 million) or more, and according to reports Bar…