I am very sorry to hear of your loss, these bandits are as GUILTY as hell. Sad to say, but you have joined the 10's of thousands of other victims of this internet theft. These so called brokers are in reality just common crooks and con men who prey on the ignorance (and hope) of the common man trying to improve their situation and they care nothing of your financial circumstances. Unfortunately the lies they tell are such that you want to believe them, and ignore the possibility that what they say just can't be true. They are not real brokers nor do they deal in the FX market. Your money, like all the other victims, goes straight into their bank account never to be seen by you again. There are hundreds of these crooked websites out there, in all languages and countries.
The old saying of "If it sounds too good to be true then it is a scam" has been ignored by many thousands of other victims who wanted to believe this would make them money. The lesson to be learned here is never invest in something you don't understand and always, but always, make sure a company is regulated by a significant regulator.
Any promise of the return of some of your funds (3500 USD) by them will never happen. So many others have been promised the same and it was always 'lost' in the transferal system and will be your responsibility to find it! These people are just plain crooks, if they operated out of a High Street shop they would have been arrested and imprisoned long ago, it is the Internet they hide behind and the gullibility of people that let them do it. Your only hope of getting anything back is to claim a charge back on your Credit/Debit cards stating that "the service you had agreed to and expected has not been received". Contact your card providers again and make a fresh chargeback claim, I am sorry to say this is your only hope of getting anything back. Do NOT use the services of 'Recovery Agents' as they are from the same scam and will charge for their service but will never deliver! Good Luck.