Q: My car reduced speed and increase at the same time even on the motion

Hi and thanks for your question. With your engine becomes jerky at highway speeds and is trying to climb up in speed but slow down at the same time, then you will need to check the EGR (Engine Gas Recirculation on the engine. The EGR takes old gasses that are burnt and puts them into the engine to reduce pinging and extra heat on heavy acceleration. The EGR can be plugged up and needs attention. I recommend removing the EGR valve and cleaning it. Then put it back on and retest your vehicle. If you have the same problem, then the EGR valve is stuck and needs replaced. I recommend seeking out a professional to diagnose the loss of power and guide with repairs.