Unable to do trading in Parallel Mafia

Hello friends, I would like to know what does the Black Markets makes. I was trying to search answer for it but no one have listed anything about it. Actually there are some of them in overcrowded markets. This was first thing which I was like to ask, so other thing is that I am not able to transfer gold, not know what problem is, is there anyone who is able to solve this issue? There is just one method for doing trading that is through Market but that is very much crowded. Whereas I had all my trades jacked more than once, so what I should do with it. Thank you.