Unstated is why Russia is letting in people from Camaroon. It's not like their economy is so overheated that they have to import workers. There's more to this than the article reveals
They come for studing in universities. They often get into financial trouble since their governments regularly fail to provide them with scholarships on time. This makes the foreign students take up illegal activities rather often. But the real reason of their position is usual racial hatred combined with the fact they aren't numerous enough to resist. The last condition is absolutely necessary for human scum, who beat the Black students.
It's not like their economy is so overheated that they have to import workers.
There are many people from very poor countries mainly from the former USSR, say, from Tajikistan. They take up (mostly illegally) in construction, on vegetable distribution warehouses, or as street-cleaners, road builders.
Russia is a poor country comparing to the USA, but for Tajiks, Georgians, Armenians, even Ukrainians, etc., it's a place where they can earn money.
Actually they're economy is growing faster than ours, and the import a lot of labor.
From the article:
Economists say immigration is necessary to offset the decline in Russia’s population, which is falling by around 750,000 a year, but experts say there is no sign ethnic Russians are getting any happier about it.