When you go to Alexa.com to check the rankings of the most popular websites in Nigeria you will get a result that is not really what you need because Alexa will include Google, YouTube, and all those sites that are not real "Nigerian website".

If the Alexa ranking is what you want you can see from their site: https://www.alexa.com/topsites/countries/NG

What I have done is to get the rankings, remove every website that is not Nigerian... the result is an authentic ranking of the most visited websites in Nigeria: https://zestmade.com/blog/top-websites-nigeria/