A mountaineer about to descend down a mountain with a blue helmet on.
A person starts to climb down the mountain before it gets too dark.
Just because a mountaineer is going to descend down the mountain does not mean that it is because it is getting to dark.
We have no idea it is about to get too dark, it might be early in the morning.
A man can climb down a mountain well before it gets too dark at other times of the day.