You can't get past the Green Hills that you slide and slip on.

To get past this all you need to do is get a crate on your trolley, then drive your trolley to the hill.

Then step on the crate on the trolley. The trolley should become highlighted.

Pick up the trolley

Make sure you are standing the direction you want to go and that you move with the crate.

You now should be able to explore new places with this cheat.