CS platform won't withdraw my money and wants me to pay taxes. It's really disgusting and unscrupulous.

I was taught by a friend who helped me to trade and deposit money. He also put some money in my account. Some of the money he deposited in this platform is not my money. But most of the money is mine. Now customer service won't let me withdraw the money, saying that I have to pay taxes to withdraw the money. What should I do? I don't have any money left. 400,000 or so dollars are in there. I'm just a woman. I don't know why I'm being treated this way.