i was surprised to see the market today, everything fell in a short time, bitcoin fell around $1000 very fast and looking at coinmarketcap, all coins are red. a few days ago bitcoin rose slowly, but today was very surprising. What happen today?

If you are new to the crypto space, I'm not surprised. But just to tell you that what you have seen today is very common in the crypto space, that's how volatility looks like and we can't expect everything to go so well, a market crash is also possible. That is why it is called a risky investment and if you can't manage to handle this situation and are able to adopt it, surely it gives stress on you.
I encourage you to keep strong and calm, it dumps today but believe it will turn back high again.
Crypto is indeed a risky investment, but it also has great rewards. In fact, we can manage the risks ourselves, but greed often gets to us and ends in cut losses. the safest cryptocurrency investment is in bitcoin, so we can place most of the capital we have, and after that we must be able to diversify according to the level of risk. that way we will remain calm in the face of existing fluctuations