my unsolicited suggestions as the mid-west nesba photographer.
#1, never shoot in AUTO mode. Keeping the camera in shutter priority mode ("S" on the Nikons, Tv on Canon) will let the camera decide how to best expose the shot while you control one of the more important settings while new, only the shutter speed.
set your shutter speed to about 1/500 at the fastest (1/1000 is faster than 1/500). Maybe 1/320 at the slowest till you get your technique down a bit better. You will need to pan with the bike you're shooting very smoothly even at 1/500 but you will get some motion blur to the wheels, etc.
Next, your focus mode is set to "closest subject", and because of that your camera is focusing on the fence right in front of you. Use the focus mode that is just the little bracket (single sensor AF) and then make sure that bracket is in the center of the viewfinder. Also, use AF-C autofocus mode. (C for continuous). The camera will track and keep the object you put in the little brackets in focus for the whole time you're at least half pressing the release button.
You have the right idea, it took me a year to get a decent track shot! Good luck!