Sure i see it now. I see where i should use AA and this really can improve this piece. Also you have right, i use too much light in some places. 

Thanks a lot for help. Soon i want add something bigger and i use your tips for make it looks better. 

(Now you should receive this message as respond)

Thanks for tips. I agree colours is my weak point at this time and still i learning how compose them better.

If you can tell me in which areas I made the most mistakes I would be very grateful.