What problems did the Congo face after winning its independence from Belgium?

Upon winning independence from Belgium in 1960, the Republic of the Congo did indeed face a number of significant problems. The first pressing issue was that the newly independent nation had no system in place to govern the country on a national level. The entire previous government had been run exclusively by Belgian bureaucrats and colonial administrators. The Belgians left quite abruptly without putting any transitional structures in place to help the Congo transition to independence after seventy-five years of colonial rule. This power vacuum at the national level meant that most rule was left to local tribal leaders, who often held old rivalries and conflicting agendas.
To make matters worse, only a week after gaining independence, the military forces of the young nation began a mutiny. The soldiers were resentful of remaining under the command of white officers. They had thought that Prime Minister Patrice Lumumba would replace these officers with Congolese officers, and they refused to serve under their old commanders. The soldiers began to harass whites who remained in the country. The mutiny ended only when the officers were replaced with black ones.
At the same time, two Congolese provinces seceded. Moise Tshombe, a Congolese businessman led the province of Katanga in its own independence movement. A month later, the mineral-rich province of Kasai also broke off from the Congo in order to protect its natural resources from the chaos that was consuming the country.
In order to protect white settlers, the Belgians sent their army back into the country. This only led to more violence. Belgium, with the aid of mercenary fighters, supported the succession of Katanga. Only the intervention of United Nation peacekeepers succeeded in holding the country together. However, UN troops did not enter Katanga. This allowed the Belgians to support the secessionist regime there.
Lumumba was forced to use his army to take back Katanga. Lumumba also sought support from the Soviet Union to provide his nation with technical and military support. This move worried the United States, which sought to undermine the Soviet presence. Now the Congo was caught up in the Cold War rivalry of major world powers.
In a coup backed by the US, the military commander Mobutu Sese Seko overthrew and murdered Lumumba. The country then descended into a brutal civil war. Peasant uprisings took place all around the country. Eventually, Mobutu emerged as the winner. Mobutu ruled the nation using brutal methods to maintain his control until he was ousted in 1997.
https://www.bbc.com/news/world-africa-13283212