assure that Germany fared better during WW1
now hear me out first.
there was no way that Germany could have flat out won the first world war, they didn't have the manpower to do it.
i would go back and make sure that the US didn't get involved, the war would have stretched out for a bit longer but Germany would have eventually lost or gone to armistice on much better terms that what they ended up with.
France would have never ended up taking back Alsace-Lorraine and in turn would have not crippled Germany's economy and industrial base.
further, Germany would not have gotten sucked into economic depression paying war reparations as well as not ended up with massive unemployment from the loss of its industrial base.
with its economy not faltering its people would not have ended up turning to Nazism to save them and Hitler would have stayed as a mediocre painter, never raising to the point of being able to control the country and drive our ancestors straight into World War 2.
Also, because America did not get involved its economy and workforce would not have suffered so greatly and possibly the Great Depression could have been avoided entirely.