I won't take your advice as bad because you showed your friend the bitcoin investment but you didn't show your friend your wallet seed phrase. My friend also showed me his investments but I never thought negative about him and he also did not keep any secrets from me. But your friend must be aware before investing that the seed phrase of the wallet he holds is very safe. It is not just about investing but also about securing investments. I want to know from you if you are active tell me if your friend invested like 1BTC? If your friend has invested one btc using DCA method then definitely tell your friend to wait till bull market.