The question of African expansion would be insignificant during the time building up to the second world war, as Germany had lost all of it's African colonies in the Treaty of Versaies to Britain and France. One could argue that if Germany had these colonies Hitler would not be able to use Lebensraum as an excuse to expand to Eastern Europe, but this scenario is unlikely as: Germany would have only kept it's colonies if it would have won the Great War, as the lengh and atrocities carried out during the war almost guaranteed a cruel treaty from the victors If Germany would have won, the Hohenzollern dynasty would stay in power, meaning Hitler would never rise.

Also, Hitler had no African ambitions, and if he did have african colonies he would most likely give them to Mussolini, or to Franco to convincd him to fully commit to WW2