for your first
it wasnt too bad!
the biggest problem i felt was the animation didnt feel fluid at all. There were wayyyyy too many blackouts and cuts between scenes. make them more fluid, show the ninja running around and his actions. in other words, dont just jump from scene to scene... show some of the "in between" if that makes sense
The other thing was the "slow motion" feel you put on movements in the animation like the ninja stars. get rid of it. making things move at the right speed in an animation might take some experience
Sound effects could use a touch up too. Add some more, or even better, ambient sounds in the background. Having one single sound like a footstep or ninja star hit in the middle of nothingness sounds weird.
hope this helped