1.How did I lose my bitcoin?
I learned about the ETHBull and ETHBear Token which is the 3x leverage token of the FTX exchange. The price of ether was then below $ 100
At that time the price of ETHBear was $ 30 when I invested.Then the price of the Ethereum was around $ 120. At the same time, I panic and I made all my investments on ETHBear in the face of huge profit.
2.Big mistake of my life

this investment was done at the behest of a youtuber which proved to be a big mistake in my life.Now I have thought that do not invest at the behest of others.
When I lost my entire BTC, I felt very bad, please do not do it.
Thanks for all
Just like you said, this situation might be the biggest mistake of your life so far but it sure did leave you wiser, stronger, and as well to always believe in yourself as trade signals from even the experts can fail any time. I believe with time, you'll be back stronger and wiser towrds taking more calculated risks