Retaining Wall Drain Do I Need A Retaining Wall, French Drain Or Both?

Do I need a retaining wall, french drain or both? - retaining wall drain

My property is slightly less than its neighbor to my right. Both of our backyards back into the forest, and shortly after the chain link fence, there is a steep slope into a creek. After heavy rains, my yard is plenty of water. I think a French drain that can help .... only on the water behind the fence along the hill near housing for collecting all of them.

These contribute to the erosion of the backyard or do I need a retaining wall to get a flat line to glide down the hill?