What were challenges African nations faced after World War II?

After World War II, many African nations saw a chance to achieve independence from European colonial rule. However, the European powers were very reluctant to let go of their imperial holdings in Africa. The war had destroyed their economies, and they counted on the resources of their colonies to rebuild their nations' wealth. This even meant that several European powers, particularly France, Great Britain, and Belgium began expanding their empires even further into the Africa's interior. More land and power was taken away from tribal leaders. Colonial administrators began to demand even more mineral and agricultural resources from African workers.
At the same time, many African peoples began the call for independence. After the war, the United Nations issued a declaration that all peoples have the right to self-rule. They were also influenced by the decolonization of Asia that was occurring at the time. Africans seized on this to demand freedom from colonial rule. Europeans found it increasingly difficult to justify keeping other nations under colonial rule. They responded by saying that they were retaining these colonial possessions for a while longer in order to prepare them for independence. In the meantime, they continued to exploit the colonies' resources and labor.
Understanding that their ability to maintain colonies in Africa would not last much longer, Britain began the process of setting up local governments that would be favorable toward them once they were independent. For example, in Ghana, the British established a governmental bureaucracy designed to support them, at the exclusion of much of the local populace.
France, on the other hand, tried to convince the populace of their colonies that they should become more French instead of aspiring toward self-rule. This was not well received, and several armed struggles for independence ensued.
Even after independence was achieved, many African nations had significant struggles to face. Most had been under colonial rule for generations and had no experience of how to self-govern. With the exception of the former British colonies that had local governments in place, administrative structures were not established when the European powers suddenly left. This often created power vacuums, where local leaders struggled to gain control.
https://history.state.gov/milestones/1945-1952/asia-and-africa