Hello Hassan

thanks for being our repeated customer.

1. you are using a revolution slider in your home page but it is not compatible with ajax page transitions

therefore if you must use RevSlider you can disable ajax page transitions in customizer -> general settings

2. plz try disabling smooth scrolling in customizer -> general settings

3. try adding the following in customizer -> additional CSS (modify first to set the right values)

.scrollbar-track-y {
    width: 8px;   /* increase the width */
}

.scrollbar-track {
    background: transparent !important; /* add a background color */
}

.scrollbar-thumb {
    width: 8px; /* increase the width  of the scroll thumb*/
    height: 8px; /* increase the height  of the scroll thumb*/
    background: rgba(0, 0, 0, .5); /* set the background of the scroll thumb*/
}