I heard that investing in bitcoin is dangerous. How true is this?

Investing money in to bitcoin is not dangerous. Just plan to invest for long-term that is the secret.
The people that invested money in bitcoins 3-5 years ago are now millionaires, that is what you too should plan for.
Investing in bitcoin is not dangerous why so many now become millionaire in investing in bitcoin. Bitcoin world is continues increasing they want to join to invest and earn money to become millionaire. It is risky but not dangerous.