Money is not hundred percent safe in cryptocurrency because of the hackers in cryptos world. This has been the major issues facing the platform, so it's not really safe putting money in crypto.
Its true, its not safe if we are sharing our private key to others people. Most hacker stealing coin in exchanger wallet and thats why we should keep our coin in our own wallet and not sharing our private key to others. If we want more safe, we can use hard wallet to store our coin