severe slippage and price different between Coopermarket and other broker non same pair and same time

I had lost all my account at 10 June 2021 using broker coopermarkets related to fdxcapital. strange things happens when I check other broker with same pair and same time.. there is no slippage on other broker. I lost $12500 and $7000 on my wife name. I just want justice for us and I want my money and my wife money back. it s a huge money for us. we borrow some money from the bank, because we want to have another income, but coopermarkets make us lost that money. please help us.