Bitcoin may be a fast and cheap means to receive funds especially from overseas, yet it isn't usually the safest or even cheapest for all. There are fees which depends on the network at that particular time, and the price is volatile too. As for safety, it protects when you have knowledge on how to store properly, yet when careless, you may lose all your money. Therefore it is good but won't be said to be the best choice for all situation.
I think you are wrong when you said bitcoin is not safe in terms of receiving money from abroad (unless you made a mistake there, otherwise you are totally wrong).
However Bitcoin is one of the fastest and secured way to receive money from outside the country. But most times when transactions fee is high and mempool is congested there will be some delays, and if you want your transactions to be confirmed quickly what you need to do is increase the fees. What you should know is that Bitcoin is one of the best way to receive money from abroad because dollar rate go naira in the bank is not the same with p2p rate. If you want to get a better rate when you receive money from abroad, what you should do is request that the sender send with crypto currency and when they transaction is confirmed and you have received your crypto, change it through p2p (I believe you already know this).
Moreover, as for safety, you are to protect your seed phrase as all cost, seed phrase are not like your fiat Bank account ATM card pin whereby if you forget them you might go back to the bank and get a new one. You actually need to know how to protect your seed phrase from third party or from losing it