Why did the germans lose so easily in the battle of stalingrad during wwii?

The battle of Stalingrad was a huge turning point in WWII opening up a new front. A huge defeat to the Germans embarrassing them. The Soviets had the advantage of the winter weather that the Germans did not come prepare for. The Germans consisted of poor quality clothing that couldn't handle the cold climates to come. In addition the Germans came to Stalingrad with a poor quantity of food. The soldiers were practically starving before battle. The soldiers stood no chance because of the differences in energy levels in the two groups. The Germans were easily overwhelmed by the Soviets. Even on retreat, many German soldiers were killed. Some groups surrendered and didn't retreat because they did not consume enough energy to move forward nor backward.

i dont know but i need points