What difficulties did the patriots face at the valley forge

The answer is cold weather and starvation.

Valley Forge was on of the largest cities in America at the time. So, with so many people in the city, the local resources were depleting rapidly. So, the lack of food was present. In harsh, cold winter conditions, they faced low supplies of food and a lot of diseases. The patriot had to deal with the cold and starvation at Valle Forge.