ok so maybe i have too many questions
 

i got the blue,green,red gem and he said to bad i couldnt trade them in and i cant do anything except dodge poles and ride the mine cart.

In the place where the commies shot a hole into the trails and the mine car jumps over that hole, immediately before the exit gate there is a three-way crosspoint.

Just ride behind that crosspoint, stop the car and ride backwards. This will take you to a hidden room with a pool and a waterfall.

From the crates which float in the pool stand immediately opposite the waterfall, then whip yourself through. You will reach a chamber behind the waterfall where you'll find a key.

Use this key in the room with the pyramid.