I thought it was pretty great for a first animation.

Some things I noticed. The walking doesn't match the ground, you've got a bit of moonwalking going on, to put it one way. As tweetytunes mentioned, some of the body mechanics could use some work.
Also, one action does not need to be completed before the next is begun. For example, he would probably still be approaching the lift button as he lifts his hand to reach for it.
Some of the actions could be faster as well.

As for the ending, I was anticipating that the suit would give him control over the elevator... you could work that in maybe.

Speaking of anticipation, look up the 12 (I think?) principles of animation and see how many you can work into your short.

Keep up the good work!