But unfortunately i loose all that bitcoin , because a scammer messaged me and he told me a ponzy scheme, if i invest 100 dollars i will get 300 dollars within 3 days through bitcoin trading, that was his offer. That time the bitcoin price was 8000 dollars.
Why do you believe in an unknown person who offers a weird promise like this? It is clearly scam, it is impossible that someone gives you free money $200 only in 3 days. You should think realistically, it is a too easy way to earn money. And you must suspect him because you even don't know him at all. Why did he directly send you a message? 
Next time, never believe an unknown person. Even if you know him, you don't give any of your coins if he doesn't guarantee anything. You are better to learn trading yourself and earn money in your own way.Anyway, how many Bitcoin you lost at that moment?
You didn't explain it above.