Doors at level 19 was blocked by a propeller, you must first eliminate the blades in order to beat the gate 19.
Here's the explanation to beat level 19:
You touch the propeller correctly, you can look for prompts small propeller on the side and bottom of the door.
If you touch the white propeller will turn blue, so you make the color blue propellers not in the side and bottom of the door, after which it will appear a circle and touch the circle to open the door on the level 19.
Step in the right by pressing the propeller you can see in the picture above.
Now continue to the 100 gates level 20 explanation, or back to the 100 gates level 18 explanation