It's true that saving your mind money in the bank comes with it own flaws like depreciation of the naira and most times network issues, but you will be making a bigger mistake saving your money in an exchange because the crypto exchange is exposed to hacked, any day anytime, unlike banks that are more secure, so if anything happens to the exchange just know that your assets are gone, if you have heard about this statement, not your key, not your coin, you will understand perfectly well what am talking about.
So due to security reasons, I will prefer saving my money in the banks over crypto exchange any day anytime.
The best way to protect your Bitcoin and other crypto asset is to store it in a self custodian wallet where only you have access to it.