如何更改徽标大小并隐藏一些Div向下滚动

i want to shrink my logo and hide some div and change menubar position on scroll.I shrink my nav bar on scroll but on shrink menuitem position and logo is not shrinking like, i want to hide my div class contact_details and change div class nav_bar margin and size of logo on righti want to shrink my logo and hide some div and