Hi and welcome to Discuss Cooking I don't know what the requirements are in Nigeria, but in the United States, a chef needs to have a lot of kitchen experience. Some work their way up; some go to culinary school. The culinary school graduates have a bit of an advantage, but they still need to work in commercial kitchens for years before someone will hire them to run it.
And if you want to own the restaurant as well, you will probably need to find investors to help pay for it. Good luck.