#2
Hardly to classify. It's just.. 21 seconds.

Ok lemme tell ye this. It's pretty easy to write something awesome which lasts 01-60 seconds. What hard, is to make a full song of at least 4 minutes worth material. Especially if you're instrumental, because people wound want to listen to diversed music to compensate the lack of vocals. Sorry, it's really hard to criticize 21 seconds.
#3
Ok, thanx a lot i'll try to make smth that will last longer)
At least 2 minutes))
#4
I'd say that it's a fairly good melody. Obviously, it won't work on it's own, but it could easily be incorporated into something else - maybe as the solo to a song, maybe as the intro. Might work as a vocal melody too, but I'm a bit unsure about that.

Mostly, I'd suggest building an instrumental out of it. You've got the basis, now start arranging. Create a chord progression for it, and use your melody as the "chorus" of the instrumental.
#5
Nashag, I glad you like it!)
Thank you for this usefull tips, now i'm full of enthusiasm to continue my work on it!
But i hsve a litle problem - i'm making music from time to time
I mean sometimes i can write smth and sometimes i can't
It's all because i don't now the music theory?
Or everyone has the same problem?