Hello! The correct answer is the second: "Russia suffered almost 80,000 casualties and 90,000 prisoners of war compared to the 15,000 casualties in Germany."
As a result of the Battle of Tannenberg, on August 30 the Russian army had been annihilated, with 92,000 soldiers taken prisoner, 78,000 wounded or killed and only 10,000 survivors. The Germans suffered less than 20,000 casualties (15,000) and captured more than 500 guns. Among the dead was Samsonov himself (of the Russian Army), who had shot himself in the head the previous night as he refused to survive the defeat to give explanations.
I hope this helps.Regards!