You have a lot to learn to use bitcoin safely, like choosing wallet, buying and spending btc etc.
Just google it and you will find a lot of infomation.
well, he is trying to suggest to you dont keep ur bitcoin on an exchange platform, there has been a case where the exchange lose over 100,000 of bitcoins and those customers till now cant get back their bitcoins. so imagine u have over 10 or even 100 of bitcoins in a bank and this bank closed down due to some fault and u cant get ur $ back. even government also cant do anything.
so suggestion to u is that keep it in an offline wallet in your harddisk and do all the coding and double coding etc so even if ur comp got hack, they still cant access to ur wallets cause there is like 3 to 4 layers of password.