Germany could have won if (a lot of IFs):
5. Either NOT do Barbarossa at all or:
  -Attack in May instead of July
What, not attack Russia, are you crazy ? Have you ever read a book about WWII ? Germans have always tryed to conquer and colonize Russia, they tryed it in 1812, they startet WW I in 1914 to try it again but unfortunately France and UK interfered it. Hitler wrote “Mein kampf” in 1920 where he stated that the goal was to conquer and colonize Russia and kill all russians, and that was his casus bellum, and that was the cause that all germans supported, thats the reason they voted on him in the 1933 election. Das drang nach Ostern. The urge to go East. Hitler had nothing against brits or frenchmen, nor did he have any territorial claims in west. Hitler invaded Poland, and then UK and France started WWII because they wanted to intercept Hitler. If Hitler had said “I want to conquer Britain so German settlers can colonize that foggy island” then no Germans would have supported him ever. Germans go to war to kill slaves, not britons. Thats the case in WWII, and in WWI, and 1812, and before that too, we can go back to the mediveal, the pattern is blatant.