The withdrawal is unavailable in TskfxI ,I want to take back my deposit by law.

The platform of Tskfx is a fraud platform,the withdrawal of which is unavailable.I successfully withdrawed $200 I applied for the first time.(But it was operated by one who introduced me to participate and the account is a private one!) But I failed to withdraw $4000 I applied for the second time by myself.It suggested at least 50 lots for each USD trading.Athough I succeeded for the first time,I can't withdraw now.In addition,it is said that the proceeding will last 1 to 3 weekdays.They wouldn't proceed it until I wrote to them.Now I haven't written to them, so it is still under proceeding(more than 3 days).It is a fraud obviously.I really want to take back my deposit but have no ideas of legal approach.