A word to the historians: The film is based on the life of the legendary Russian sniper. As I understand it, is not entirely clear to what extent this told the whole truth in his memoirs. There are contradictions, and it may well be that the war propaganda exaggerated his successes.
However, I doubt that this film is based as absolutely authentic, proven on 100% fact. I think the goal is entertainment, based on the story of a Soviet war hero, no more and no less.
Even if the life of a real sniper proceeded quite differently, the duel depicted in the film two snipers in the middle of a war zone is entertaining in any case, even if the end and the unnecessary love story may not be optimal.