Everybody needs to fear crypto exchange without waiting for people to preach exchange is not good for storing bitcoin. Remitano exchange is where I do buy bitcoin and sell bitcoin. Sometimes it is very difficult to have access with this wallet to sell or buy bitcoin, at times it takes 24hrs before one can logging this exchange. Just imagine exchange like this have some network issues like this and never gets back to normal again. This should be enough reason why people shouldn't store bitcoin on exchange wallet.
Remitano? They are like the Paxful platform but very worse, why use them when you can just use Binance exchange? You can use Naira to buy bitcoin on Binance exchange and move to your hardware wallet, stay away from Remitano, they also cheat when it comes to fees and Naira to Dollar value, worst P2P service ever.
Please learn the difference between a centralized exchange and a decentralised exchange, it seems that you don't know the difference and it is very important for a newbie to understand this.
Also there is a difference between a closed a source crypto wallet and open source crypto wallet, you need to do your own research on these.