It will suffice to tell him that trading in cryptocurrency market is risky and that he must carefully control the risk. In addition, if you specify that he should have knowledge about the market, follow the news and do his own research before taking any action, there will be no situation where you have to take responsibility.
It is also necessary to remind your friend to trade in the cryptocurrency market with his savings that he does not need in short or mid term, because a beginner can lose all his savings in cryptocurrency market as a result of greed, and this can hurt him a lot.