I am curious on how the African kingdoms have been, do you have a good non-biased source for that?

Unfortunately, not at the moment for Classical African history. It seems to me that you'd be better off reading older sources, or simply having to dig through biased sources and filtering out the horse shit. There's bound to be African History chronicles prior to 1960. This is partly due to the fact that modern racialists are obsessive about trying to identify a Wakanda for Africa, but for the reason I mentioned, African history is fairly decentralized. The empires existed, they were even occasionally economic power houses outside of the Sub-Sahara or East Coast. The good, but biased, historians are forced by evidence to recognize that the narrative around African history doesn't make any god damned sense, but a lot of information is simply difficult to get a hold of. This means that for Classical African history you have to do a proper deep dive on African history. No general overviews, but actually digging through the weeds of the introduction of Islam, Christendom, ethnic conflicts between the different people's of Africa, and the known history of the East Coast from Chinese, Indus, and Pacific traders.

For example, I have a Nigerian novel written prior to the 1960's, and it was written in a kind of Nigerian-English vernacular. It was popular in Nigeria at the time and was a big diversity assignment that our SJ advocation was supposed to expose us to. Unfortunately, the reason it was popular was because many Nigerians in the 1950's could relate to it, not westerners. The novel is a story about the life an times of a kind of high-status man in a semi-tribal environment who has enormous flaws and leads his family to ruin through his aggression and emotionality. There's a passage in the book which references one of the more egregious acts the man did was beat his wife on a holy day for a goddess which mandated no violence during the day. The narrator pointed out that his behavior was egregious because it was a harsh beating, and specifically on a holy day. Not that beating your wife was particularly wrong. In fact, there's a portion of the book which goes over the fact that the wife had tried to escape beatings before and the village had to step in and calm the asshole down because it was getting out of hand... and normally for stupid reasons like 'the food wasn't ready', or 'she said something that insulted my honor'.

That's not exactly Wakanda now is it?

The Nigerians related to the story because it tells of a tale of what a lot of Nigeria had been like only 100 years ago or so. This was a story about their grandparents. Turns out "Negrophilia" is stupid. Fetishizing blackness is retarded. It's a weird thing that white people do, and the Africans, don't. Africans are a people much like anyone else, and they were living on a continent that wasn't easy to develop.

White SJWS: "Africa is filled with beautiful cultures and people!"

Black SJWs: "Yes it is! Kill yourself!"

Africans: "This place is nice, but our lives kinda suck. Sometimes it sucks because the Zulu are fucking asshole savages and ruin everything for everyone. Fuck them. I'll take any white person over a Zulu any. day."

For a good overview, I'd argue Thomas Sowell (Conquests & Cultures, and Immigration & Cultures are excellent, but he has plenty of books on Race as well) and Jared Diamond (Guns, Germs, & Steel and Collapse are both good). For a generic overview of why Africa is the way it is, they both run along the same path and it's why SJWs fucking hate them and try to discredit them.

When I think at Africa I think of war-leaders and primitive dwellings not castles, roads, organized warfare, sewage systems or arts.

War-leaders, yes.

Primitive dwellings, yes... but that's on every single continent, including Europe. Peasants live in pretty fucking rough conditions.

Roads: there were definitely roads in any place with significant trade. Which is basically North Africa and the Horn of Africa. Islamic colonization of Northern Africa and the transportation of raw materials (like gold) out of Northern Africa required significant infrastructure. There were times when Northern Africa surpassed European development, particularly on the Iberian Peninsula. The Horn of Africa had a massive trade network through the Indian Ocean, so they've had powerful city states, but they never needed full-size castles because there were relatively few significant wars. If the Ottomans & Persians monopolized access to India and China, anyone on the Horn of Africa was not willing to jeopardize a precious sea-route with conflict. The Chinese had their own internal struggles to deal with, the SE Asians were willing to tolerate Chinese trading expeditions, and the Indians (again) had their own internal problems. The Islamic Arabs wanted to profit from both.

Castles: As addressed: there wasn't a huge need for your typical Asian or European Castles, and remember that population density has a limit before malaria starts slaughtering people. Earthen and timber fortifications did exist, even in central Africa. But remember it has to make sense: no livestock animals means you can't use horsepower to drag heavy things, which means you need huge sums of people, and you need keep them from dying of Malaria. There were more traditional castles... but they are always is Islamic controlled territory, mostly because the Muslims were constantly going to war and needed fortifications. From the US Marine Hymn: "The shores of Tripoli", that's in Lybia. Islamic Piracy meant the US needed to break Islamic fortifications to stop the attacks.

Organized warfare: This is where you'd be seriously wrong, and the British made the same mistake you did at isandlwana. It's not classical European organized warfare, but the level of organization needed to command and time the attacks of multiple units numbering in the tens of thousands at a time, over a massive area is a major feat of logistics and organization. Under-developed in weapons, sure. Not under-developed in tactics or discipline. A thousand Zulu warriors sneaking up on your position while using the terrain as cover from enemy observation is an amazing skill. African populations weren't totally unfamiliar with war (again, see Islam), and even the Sub-Saharan ones wouldn't be a joke.

Sewage systems are actually super fucking advanced for most civilizations. It's not easy to build or maintain a good functioning sewer-system. Rome, even in the Roman Empire, was lightyears ahead of everything else. In Pompey, sewage flowed openly in the streets. It's why roads were depressed: it allowed sewage and rain to flow down the roads. Meanwhile they built little brick crosswalks at the same height as the edge of the road so you could walk over the flowing waste water. Even a thousand years later in Europe, the sewage for castles was a literal poop-chute to the outside.

As for art. Eh. Art is art. Make of it what you will.