Stalingrad was when the decisions of our best general started to make a real contribution to their ultimate defeat.Nope.
lend lease was a tiny trickle in 1942/43, More us trying to show willing, rather than any strategic effect, only really getting into its stride in 1944.
german defeats Moscow 1941, Stalingrad 1942, Kursk 1943 were home team.
Germany was effectively out of the war after Kursk in Mid 1943.
they had lost their entire strategic reserve and never regained the initiative..... Berlin was the inevitable next stop for the Soviet Army.