Yes, I have but it didn't turn out as good as expected because the friend I was telling about investment in Bitcoin, had to invest with their last money in bitcoin, hoping that it would give huge profits within a short time, not knowing that the crypto market is unpredictable. It can make one a millionaire within a short period if only they invest wrong
First of all Bitcoin should be kept for long term investment and if someone wants quick profit then he should choose certain altcoins instead of Bitcoin. If your friend accepts your advice about buying Bitcoin then he should wait longer and should not blame you because you just share your thoughts the final decision was taken by him as no one can force anyone to make Bitcoin investment.
One should learn about Bitcoin first instead of blindly trusting others and if someone accepts his friends advice then he should not regret it in future because his friend can only give him advice and no one can completely follow the instructions of others.
First of all, let me say that, in as much as Bitcoin is the front runner when it comes to crypto currency, being the foundation on which crypto is built on, it's important for everyone crypto lover to hold bitcoin, but not mandatory or a must, and in terms of holding for a long or short term, or even buying and selling it for daily and momentary profit, that's solely at the discretion of the person, it is never a must to hold bitcoin when you really don't want to, or think there is some Altcoin with better potentials than bitcoin you should be rather holding.
And talking about advice, you are right anyway, we advice based on our knowledge which is what we know, and the last decision is always at the discretion of the person being adviced, this is why it is always important for a person to always go into doing his or her own research, in other to determine what to do and what not to do on their own.