...
Please anyone sell me
BTC500 at market, off-exchange..?

I cannot help. I am holding although these bears are making it very tempting also for me to buy. I would suggest Second Market
https://www.secondmarket.com/. They
may be able to help.
Edit: I am more convinced than before that your trendline errs on the side of predicting a BTC/USD rate on the low side and can lead to a premature sell indicator.