For a first 3D animation, this is actually pretty good. I expect great things from you dude.
The only problem with this animation is that the fighting is too slow.
A real robot or ninja would not take 3 seconds to punch the enemy. You should repair that in the next one.
Beside this, very detailed scenery for a "blocky" animation. Is just weird that the ninja looks like that Pixar's lamp with a mask and glasses, but I'll not complain this.
It's a okay animation, but you should put a bit more work next time.