I'll mention the solution here for those who have same problem as me
I'll double checked my entire Js code, and I was sure that it's completely okay,so I thought that it might be the css!
and I was right
I had to hidden the overflow because of the wrapper width (which is more than the viewport), but my problem was,
I've accidently set the overflow property to hidden for both my "BODY" and the "Wrapper" which is wrong,
and when I removed the overflow property from the wrapper, it works Perfect xD
anyway,
Thank you Carl , because of your fast answer;
and sorry if I took your time, because of an accidental issue.
soheil22's post in need help with Animation Scrollto with tweenMax was marked as the answer