Never send proof of funds such as bank statements or MT760/MT799 bank guarantees, along with government issued identification such as passports or identity cards. They will be misused.
Scammers will also attempt to scam sums of money incrementally. Never ever send any amount upfront, even if you are presented with tall words or impressive credentials such as a mandate to sell bulk bitcoin at a ten percent discount which sounds suspiciously rounded. Bitcoin being volatile and rates often fluctuating between exchanges, I would expect a legitimate trader to carefully consider margins and balance them against the market price.
Fishy.