At the Terracan, moto light is used for a short period of time….Help

Hello together !!! Hope you can help me…Have now completely new the Terracan from a dealer…Bj 2004…Automatic…of course used purchased…Now lights up the engine light when giving gas from about 50 km/h, but goes straight back out…have called the dealer who told me he knew about it (only we had not told it ) he was read out, but no error message…. Noticed us….strong acceleration…black smoke…short motor light…and sometimes a jerk.. The dealer told me to go back….but I’m so scared that he’d hit us soooooo….have fallen for a dealer…who sold us a car…6 months later…gear damage….Can anyone tell me something, or does someone have ideas ???? Who good if I could say anything and I’m not completely blind… With kind greeting