Their purpose is to earn your 5800 yuan.
Don't trust them.
They will buy stocks that will be recommended to you one or two days in advance.
Then ask you to buy their shares the next day.
If many people buy the same stock at the same time, the stock price will naturally be pushed up quickly. And they rent it to you at a high price, and the stocks they bought that day can't be sold that day. So they can make your money quickly.