Why is so hard to convince people that forex market is profitable in my country Nigeria.

It's simply because if the narrative that a huge percentage of traders are not making profit. Then add the fact that many forex firms involved in investment scheme folds up every now and then because of greed. Furthermore, most of Nigerian traders take forex as a get rich quick scheme thereby making mistakes and loosing money as a result.

Foreign currency trading does have inherent risks. A lot of people get into it without a good understanding how margin works. While margin empowers you to purchase more, it also increases your risk exposure. It is really really important that you don't overleverage your account, meaning have buffer margin that is not being used to hold an open position available. This allows for you to be able to withstand the swings in the market without having your positions liquidated.

the beginner article here is great https://forexwithanedge.com/ultimate-beginners-guide-to-forex/, at forexwithanedge.com, Its very insightful