This is your first one? THis was really really good! It takes a lot of people (myself included) years to get this good at it! The only thing wrong really was the flicker, and even I still struggle with that. This was a very creative way of showcasing your new set! I especially enjoyed the bit where the minifigure threw the knife at the hand. The sound effects were spot on as well! When I was six, I had a nightmare about a talking alligator, and it sounded exactly like the one in your video, so I’m not sure if that’s positive or negative....
Well done!

What an incredible first animation! And a fun way to showcase your new set. My favorite part was the cop jumping/sliding across the boat.
You're ready to dig deeper into the principles of animation and bringing greater detail to your already smoothly moving characters. What I recommend looking at next is gravity, specifically, how things speed up as they approach the ground, and how each particular thing bounces or falls flat. The classic animation exercises of animating a bouncing ball or a falling flour sack are very famous and should be easy to find. Study them and try them out in stop motion. Try them out with clay to get a feel for squash and stretch and how the volume of an object remains consistent, even when they squash or stretch. Then see how you can apply that to lego models doing similar actions. The illusion of weight, and of effort used to lift that weight, are one of the "Holy Grails" of animation, that we all hope to be able to achieve.
Also "anticipation and follow-through" are never to be underrated, and something I think almost every animator can pay more attention to.
Excellent work, and welcome to this bizarre and wonderful craft!

The best example is to watch a pitcher in baseball. The ball doesn't just fly out of his hand, there's this big fantastic wind up, and then after he releases the ball what does his body do? Exaggeration is another principle of animation, so making the anticipation and follow through really clear and exaggerated makes the motion very clear and entertaining.