Heya veepee, welcome to Bricks in Motion! \o/ \o/ \o/
The animation test is quite good, and it looks like you have a solid setup for brickfilming. Great camera quality, no light flickering, no moving/jittering of the camera... you've managed to avoid the biggest beginner's pitfalls! The animation looks pretty good, especially for a first effort. Helix and Robukka have have given some good advice so far.
Something to keep an eye on while animating is making sure that the upper body doesn't randomly move around between frames. One frame he's leaning forward, the next one backward, the next he's straight again. This jittery movement is hard on the eyes, and makes the animation look choppy. For the running, don't be afraid to use bigger movements! Throw the legs up in the air, let those arms swing a lot more. In the part where he's walking toward the camera, he sort of "hops" for one single frame (I think that's when his legs are between the studs?), which also looks a bit choppy. It might look better by having him be a little higher for the next frame so that the bouncing flows a bit more natural.
Don't feel like you need to work on all these things! I'm nitpicking a lot here. A lot of these things become much easier the more you animate, to the point where you don't even have to think consciously about it. Practice makes perfect!
Last thing: Helix mentioned "sticky tack". In the Netherlands (and Germany) the goto product for this is Pritt Poster Buddies. I don't know if they have this exact stuff in Finland, but you can probably find something similar at an office supply store (usually close to the thumb tacks). The regular use is to stick posters onto walls. It's sort of a sticky clay, almost like chewing gum. It's very handy to keep minifigs from falling over, and has all sorts of uses.