BTC has fallen too fast. What do you think about the current market? Should I wait for BTC $ 8k and buy?
I doubt it very much. In my opinion you should have bought at $13k or even right now. Below $16000 should be a good value to start buying for the short-medium term, assuming that the correction comes by the end of the year.
The best strategy is actually buying a bit at a time instead of trying to time your entry point completely right.
Let's face it - at the lowest point you're probably going to freak out and not buy any, and try to wait a few more days. It's almost impossible to predict what the low is but it's certainly not going to be below $10k for this time.
Start buying with 20% of your capital every single day, for 5 days. That's risk minimalisation for you.