Translation of ergötzen

A bystander who watched the entire scene all the time decided to help me. He was an older man, around seventy, but nonetheless he went to the oldest of these kids and slapped him. The boy was sixteen.
It is an abandoned place in the middle of Spain, in the middle of nowhere. The station is located near a junction where the ways of the trains split. Both are split as well, in their minds.
We walked by waterfalls and rivers, but the water was too cold to swimm in. The hike made us tired and we were in the valley, which meant that we had to climb up again. The climb was difficult.