Other mistake: During the first fight scene just before you see Gege accidentally shoot his friend, Fritz goes off with another German to look for Russians. However, as he sets off you can see that he has no bullets in his gun at all! There is no magazine attached. (00:27:25)
Factual error: The Germans encounter three enemy tanks, all Russian T-34/85 models that were introduced in mid-1944. Additionally, they shoot at the tanks with an anti-tank gun which is painted sand colour. This colour was not introduced until Feb 1943.
Answer: There are multiple Russian tanks in the movie. You have to be more specific about when.
lionhead