In the general.html file of the theme

you can find these lines: 

var time = 400;var distance = 300;

or you can just remove this function at all:

<script>if (window.addEventListener) window.addEventListener('DOMMouseScroll', wheel, false);window.onmousewheel = document.onmousewheel = wheel;
function wheel(event) {var delta = 0;if (event.wheelDelta) delta = event.wheelDelta / 120;else if (event.detail) delta = -event.detail / 3;
handle(delta);if (event.preventDefault) event.preventDefault();event.returnValue = false;}
function handle(delta) {var time = 400;var distance = 300;$('html, body').stop().animate({scrollTop: $(window).scrollTop() - (distance * delta)}, time );}</script>

I see you have added a review and indicated this as the problem I would really appreciate if you change the review. Thanks

It works !!

thanks for your support