No problem! :D

Thanks for wasting 6 minutes of my life!

@CyclopsDragon|Wumboligist: Thanks for the way to fix the checkpoint. I'll get to work on fixing these issues, and thank you for the advice!

A few quick tips.

Falling of the track when going too fast is a sign that your track is twisting or looping too quickly. In general, if the track is twisting or looping away from the car, it's best to have very smooth movement.

Boost management. Many players see it as a challenge to try to boost through the entire level, and certain track shapes, especially long upside-down sections when flying is disabled, make it nearly impossible to recover boost. In these sections, it's generally recommended to use a power ring to give the player some boost back, unless you're specifically trying to make the player slow down. Upside-down checkpoints are not recommended in most cases, so don't use those instead of power rings.

At least one of your checkpoints is pointing backwards. This is a simple fix: just find the blue arrow when you select it and align it in the direction you want the checkpoint to face (or use the "rotate 180 degrees around local Y" tool).