I guess this is a fantasy coaster but idk. On the mcbr, you shoul have no magnets. Instead just tilt it so the train would roll off if stopped. Like the others said, the turns needed banking and shaping work. Your hills, thought they gave nice air for a short time, didn't hold it. I can see it giving a little but you went from -1.1 to 0.5 in no time. The air over the lift hill would be very fun, but would the chain/cable still stay attached? Supports looked good on the lift/2nd hill and one other hill with the same style supports, but the overbanks looked bad. You had beams stretching 75(complete guess)or more feet to connect the track. In the first helix, the support system was way too morgan. Spread those things out, you've got 4 spine track so its fine. Speaking of spines, the whole thing is 4 spine and whil it reminds us of TTD and KK, its not needed. Tall hills yes, end hills no. With the 3ds, maybe add some color to the walls? Tests tubes would be cool. In the graffiti, try to get the texture of that to line up with the normal wall texture. Yours goes from big grain on text to tiny grain on wall.
I say most of that from a realistic point of view, if its fantasy, take that into consideration lightly.