hi mahmoudnahmad ( we gotta come up with a nickname for you, thats alot to type! )
yeah, i agree with everyone else, it does seem a little early to be calling it a demo reel, but good for you for putting it together! everyone was there at some point, and i've still never modelled a car, and if i did i doubt it would look that good.
as far as what i saw on your reel, the things i liked the most were the car and the opening camera move. even doing little things will make it so much better. for example, the gears that are turning in the beginning - bevel the edges of them and put a glossy material on them. it won't be anything spectacular, but it will at least not be a grey shaded flat model. and the dominoes - was it ar lutik who said they were "15 second modelled"? i agree, they look pretty simple, ESPECIALLY in the same shot as your car! i'd say keep them seperate. that way, if you just show the dominoes, people can focus on the dynamics of them hitting and toppling each other, and not be distracted by the car.
and it really bugged me that there were no shadows under the car. it looked like it was floating. your character rotations looked like they were touching ground, so i know you can do it!
still, i'm glad to see you cranking stuff out and learning like crazy! keep it up! and you've come to the right place to learn, since there's no 3d community where you live. ask for tips anytime!