It's true that it is not recommended to give money to anyone so they would trade for you since they can easily ruin your investments the best thing to do is to figure out which strategy and coins would work for you also it's important not to focus just on one coin but it's better to divide your investment to different portions. There are some tutorials available online for free where in you can learn different strategies and maybe you can figure it out which strategy suits you.
The thing is, even if you do trust them and you end up giving them the money and they do not steal it, there is a big chance they are not as great investors as they claim to be and that is about the biggest problem there is.
We all know there is a huge risk that if you give your money to someone, they could potentially just take that money and leave, which would be the biggest possibility but people are smart about it now, they do pick people who will not scam them better compared to previous years, but even with that, you could still give your money to someone trustworthy and they could just bankrupt you.
I have seen people who invested 100 bitcoins that went down to 80 bitcoins after just a month, dude was a legit person but he just made a horrible investment.