Div Positioning

I have created a second menu on the right hand side with a similar cascading effect as the sidebar:

https://www.safrestaurants.co.uk/shoreditch/saf-shoreditch/food/

It has been put within a shoreditchfood div with the following properties:

.shoreditchfood {
display: block;
position: relative;
left: 513px;
z-index: 50;
top: -270px;
width: 134px;
background-image: url(‘https://www.safrestaurants.co.uk/shoreditch/wp-content/themes/child/images/menu-opacity.png’);
}

However the position of the div is inconsistent across pages and posts on the website. On the two ‘Drinks Menu’ pages the menu sits outside of the website height and isn’t even visible.

Any ideas what is causing the problem?

Thank you in advance.

Laura