What you are doing here is also a challenge for your cameras auto focus system (if that is how you are doing it).
Camera/lenses in servo auto focus mode that could keep up with what I imagine to be the speed and agility of these little cars, live at the high end of the camera range.
The good news is you can over come this with practice, skill and planning.
You want to play around with the time honoured skill of pre focus.
Rather than have the camera struggle with keeping the subject in focus the whole time, (I'll use picture two as an example) prefocus in manual (or single shot auto focus and switch to manual to hold the focus setting) on a point just past the bit of rope that forms the apex of the corner. You are picturing the shot you want and staging it in your mind then preempting where the point of focus needs to be to achieve it.
Now just take repeated shots of cars clipping that apex till you think you have what you want then move on to staging the next shot.
Say that shot was the picture four scenario, you might pick the line on the track in front of the white car as your focus point. The car is about to cross that line, click.
Those cars are coming at you with speed so check your preview to see how much they moved towards you between when you made the decision click the shutter and where they ended up after a bit of reaction time and shutter lag.
Use that as a guide as to how far before the line to make the decision to click so as the capture happens on the line and therefore in your field of focus.
This is assuming you have an entry level camera and even if so don't get the impression from this that its servo focus is not useful because it is, it is just that what I am seeing here (more particularly the cars travelling towards the camera) is a bit beyond the design brief of such a camera.
I just came from a post you made about being a beginner and not getting helpful input so I hope this gives you something useful.
Some cameras can track focus and blaze off up to 12 frames per second, but where is the challenge in that.