I don't know if OP wants to trade bitcoin with a friend or with the help of a friend, because he said that he wants to trade it "through" a friend and that can mean 2 different things.
If we're talking about selling a friend your bitcoin, it's completely fine, just remember that a friend can also steal from you and stop being a friend, but the money will be gone.
Make sure you check if the money is real and secured before you send him BTC.
If we're talking about your friend helping you trade your BTC, I think that you shouldn't do it. It's an easy task and you can do everything yourself. Don't let others between you and your money.
We have to make sure that it is a friend we trust to avoid problems between us. A good friend will not cause problems for us and will remain a good friend.
Before making a transaction with a friend, we must ask what they want. We can also make sure we have Bitcoin and he also has his money. If everything is clear, then we can make transactions with friends.
Actually, this is not recommended even if it is your own friend. Since of course investing in bitcoin is about money, people's minds are very changeable and we will never know. OK, let's assume that currently there is a friend who can be trusted, but we don't know that if bitcoin increases significantly and profits double, he might steal our money or bitcoins. So the risk is very big trusting investments in other people.
The best step is to invest in bitcoin independently, even if you don't understand or don't know how it works but really want to invest in bitcoin, it's better to learn first. And it would be even better if your friends understand how to invest in Bitcoin. Learn with him instead of trusting to trade your bitcoins to your best friend. Apart from that, entrusting your trading to your own friends carries a high risk, you could lose your friend if he makes the wrong investment decision, causing you to suffer a loss.
We can direct him to buy Bitcoin on an exchange if we really don't want to transact with it or have concerns about the safety of the Bitcoin we own or even ourselves. Everything will depend on the situation and conditions at that time so that we can adapt well.
By teaching our friend to buy Bitcoin on the exchange, we can at least open his mind to the possibility of buying his Bitcoin directly on the exchange without us needing to know. He can learn investing or trading after we explain more to him.