Hi,
Open this CSS file:
www.roldeco.cz/modules/mod_flexible_vm3_cart/assets/css/theme1.css
find this CSS rule:
#FlexibleVM3Cart .flexible_cart_products{margin:10px 0 15px 0;padding:10px 0; border-bottom:1px solid #aaa; max-height:500px; overflow:scroll;}
and replace it with this:
#FlexibleVM3Cart .flexible_cart_products{margin:10px 0 15px 0;padding:10px 0; border-bottom:1px solid #aaa; max-height:500px; overflow:auto;}
This should fix the problem you have (scrollbars will be hidden)
Regards.