Germany had been winning in Russia, but that battle was literally hand to hand for every square inch that the Russians fought for. The entire population took part in defeating the Germans and it was a turning point for the Russians. Even today when you visit Russia they point out to you sites where they fought the Germans.
There may be several ways of answering this question. For instance, it could be argued that the destruction of the Graf Spee in 1939 was Germany's first defeat. I would say that Germany's first significant defeat was at Stalingrad in early 1943.
2 February 1943
1942
The Axis never won Stalingrad which was a significant defeat for Axis forces from which they never recovered .
Russia defeated the German Army at the Battle of Stalingrad (February 2, 1943) .
The Axis powers never won the battle Stalingrad which turned into a significant defeat for the Axis forces from which they never recovered .
The loss of the German 6th Army at Stalingrad marked the furthest the Wehrmacht would go on the Eastern Front . It was significant morale booster for the Russian Army and the Russian people . The Germans never regained the initiative on the Eastern Front .
Stalingrad
The Axis powers never won the battle for Stalingrad which turned into a significant defeat for the Axis forces from which they never recovered .
The Battle of Stalingrad was a pivotal event for Germany because it marked a major turning point in World War II. The German defeat in Stalingrad not only halted their advance into the Soviet Union, but also resulted in the loss of a significant number of troops and resources. This defeat deeply demoralized the German army and undermined their confidence, ultimately leading to their ultimate defeat in the war.
The Germans came to grief in Russia at the significant battle of Stalingrad from which they never recovered ; the battle for the city was from 17 July 1942 - 2 February 1943 .
Yes , the public became aware that this was the first significant military defeat of a German army by Russian forces .