Undisclosed information and nothing stated on the Derka Report

I am disappointed at WE BUY Cars. 18 Jan 2021 I bought a car at Silver Lake branch and when I test drove it showed Transmission - Consult workshop andI asked the sales person and he said it's nothing serious it is due to low oil in the gear box and the Derka Report did not state any faulty with engine . Until I drove my kids to school, I noticed that the car is using too much petrol and jumping gears as it is an automatic and I felt I cannot afford the petrol anymore . I went to We Buy Cars to try to trade in for something affordable and they told me they can't take the car as it had Gearbox fault. I had this car for a month now and don't use daily as I am working from home and never traveled long distances. I use the car on weekends to go to the shops and surrounding areas. The Derka report didn't indicate any gearbox issues otherwise I would not have bought it. So I was told there's is nothing We buy Cars can do i must lodge a complaint and someone will contact me. Honestly, I don't want the car anymore. We buy cars, pls take your car back as I don't want to inherit your problem and make it mine. I am a single mother and don't have the money to fix the gearbox on a Mercedes Benz. You bought the car from the previous owner with this problem and never disclosed this information to me so I can make an informed decision. This is not right!!!!.This is just so pathetic yooooo....

I am so disappointed especially after I reading the reviews and was convinced I would get a good and fair service.