Unfortunately, it is exchange services like https://changelly.com/ that encourage these platforms to continue operating and thus scam investors.
HitBtc are selective scammers and therefore they will deal with you, create an account, trade until you deposit a huge sums, and then you will come to the office and the arguments in order to steal your money.

I am sorry for your loss, but I think you lost twice, the first with money (2.3 BTC) and the second by sending the documents as they might have sold them.