Challenge 1 - Skate forwards and jump onto the rail, then jump off again onto
the train below, Simple. It doesn't matter if you hurt yourself either.
Challenge 2 - Turn right and head up the stairs, carry on until you get to the
roof. Jump onto the spiral and grind down it, jumping of at the end and onto
the drain pipe (This can be a little tricky). Then jump off the end and land on
the roof.
Challenge 3 - Skate towards the ramp and grind up the side of it. Jump off and
land on the correct cable (the third one, this is very difficult to do!), then
grind along it before jumping through the gate.
If you are having difficulty doing this then try my alternative method:
SKATE up the ramp and get onto the center (use a cable to grind to it). Then
turn round until your facing the right cable (you should see the gate in the
distance) and grind your way to victory!