Adding div to page template is breaking the page?

Hi Guys,

Im not great with php and didn’t develop this website. However I’ve ended up doing some small changes to it.

I’m trying to add a grey sidebar underneath the product navigation to the left. I know i need to add a div to the page template, however when I do this it makes the page not appear, just a white page when you try and load it.

Here is the page template code.

https://pastebin.com/raw.php?i=ZXurWb8r

and here is a link to the page im trying to edit.

https://www.askas.co.uk/products/