I'm glad you found a way to spice up the first course from Mario Kart DS.
The lack of scenery I can excuse since this is meant to be a simple course, and the same goes for the shortcut, though awkward as it is.
However, having two sets of speed-locked boosters is a little overkill, especially if you're trying to catch up on the last lap via the shortcut. Regular boosters would work fine in both places and changing the off-road on the shortcut to some pavement would be a nice touch.
If this was your first course, I'd say you did a pretty good job; I look forward to seeing what else you make.