The world map is changing: The UN has backed replacing the 500-year-old Mercator projection with the accurate Equal Earth projection
(thelemmy.club)
The center - east to west - is 0 degrees longitude, defined as the Royal Observatory in Greenwich, England. This does also go through West Africa
The center - north to south - is 0 degrees latitude, defined as the equator.
Because of this, Africa is central on the vast majority of world map projections including the Mercator and the Equal Earth.
Accuracy is relative. The Mercator distorts areas bigger the further away they are from the equator. This exaggerates the size of the USA, Europe etc compared to Africa.