This is your first time animating an armature and dealing with different interpolation modes.
Sounds difficult, right?
Nope. It's super easy!!
Animate the armature controls (bone shapes) from the screen left to the screen right and back again.
Each shape should use a different interpolation mode. Constant, Linear, Bezier and then User's choice.
You should try to make the top 3 shapes arrive at the same time (excluding the last shape because it can be random)