Classified business model is getting outdated. There are quite a number of sites out there offering similar services. However, I believe you should be able to create a niche classified website where people can only exchange a single item such as mobile phones or laptops. Also, you can limit the location to only Lagos. If you really want to be different from others, you can create a pick up and drop off locations within a given radius and offer product verification as an additional service. (Provided OLX isn't doing that already)
Btw, the website layout is good.