The terrain of Dusty Desert actually matches that of Arid Heights. The difference between the two is the lack of green areas in Dusty Desert.
Roller Coaster 5 is extremely easy. Do not lengthen the lift hill! Then, make a vertical drop, then make a vertical hill until it gets above ground and drop it again. Now a banked U-turn (mid-sized turns) and up 6 "humps" (up then down) and another banked U-turn and add 2 more Humps.