The hike to the nyiragongo crater is but an exhilarating one but totally worthwhile. You need reasonable amount of fitness. The trek takes about five hours depending on your fitness levels and approximately three hours to get down.
For those who have low fitness levels it could take up to 12 hours and you will have to spend the night in one of the 12 cabins. There are also those who make it in as little as for hours. The trek is tough but doable.
If you can walk around 15 miles on flat ground without stopping, you should have a high enough fitness level to make it to the top. The rangers along with the porter are great help and will also encourage you.
Given the intensity of the hike your ranger will allow you plenty of rest during the hike but beware not to rest too much and lose momentum.
Drinking a lot of water helps a lot both to keep you hydrated and energetic especially if you are hiking in the sunny season.
The hike is mostly on solid rock and a few shaky rocks so look out and a pair of good hiking boots will be a good idea.
If you are still asking if the hike is hard I would tell you yes but it is doable and worthwhile. Even more rewarding is peering into the volcano standing just at the edge it’s like enjoying a nonstop bond fire and even more rewarding is the sights from the top of the volcano’s, sunrise and sunset.