That is a problem! Watching all the videos in the world will not help with that only practice will. Hang in there with a little practice it will become automatic. But you do need to practice. As far as changing the focus point. I use a single point and very rarely move it from shot to shot. If I am shooting sports for example I put it where I want my subject captured. For most sports it is usually one point down from the top and one or two points to the left and lock it in that usually keeps my subject off center using the rule of thirds. Then I use afc on nikon and keep that dot on what ever I want to capture and hold the focus button down and let the auto focus do the work. You can also try using a group of points but keep the number of points low like 5 or 9 never more. Definately watch Steve Perry's videos. He does a great job of explaining the how's and why's as well as the different techniques. I refer to them often, kind of like a batter going into a batting cage to work on their hitting. I promise you if you stick with it and practice you will never want to go back once you get it. And like learning to ride a bike once you "get it" it will be second nature. Good Luck!

Hi Jules I don't know if your question was directed at me or not. I am not familiar with the D500 I shoot with the D7100. I know the D500 has Nikon's newest focusing system and is more sophisticated than the D7100's which is pretty darn good. I am gonna guess that you might be using the 3D tracking or what I think they call matrix mode. I could be wrong on what it is called but it is where you lock the point on your subject and the camera tracks it and moves the focus points. I never use that because it gets easily confused. Especially in low contrast situations or where the color of your subject is not distinctly different enough from the surroundings. I use single point and lock on manually to my subject and pan with their movement keeping the focus button depressed. Steve Perry has an excellent video on this very thing and goes through all the different modes and how they work.
Maybe someone that knows the D500 could answer this better.

I am not sure about whether there are cameras that require the BBF to be kept depressed while pressing the shutter button every time. But for me [Nikon user], the whole point of it is to get the focus, release the button to lock in that focus, then take as many photos as I want [usually from a tripod] without the focus changing! However, if I want to photograph a moving subject, following it with the camera, the BBF is kept depressed while shooting so that the focus will keep changing according to the subject's distance from the camera. [This also requires having settings in the camera selected for continuous AF.]