Shop Spot Pro – CSS Assistance

Hi team, I have recently made my partner's site live. I really like this template and have changed the CSS quite a bit, but I have a few little niggles that I'm struggling to solve. 1) Amend 404 page Example URL - https://www.rachaelholmes.co.uk/123 I would like to amend the 404 page to remove all widgets on the right hand side of the page, so this page just has the large "Search a keyword" search box and text above it centred in the page.   2) Add underline to dropdown menu in desktop view. If you hover over "Portfolios" it has two sub pages. I would like to improve the look of the grey drop down box and add a hover underline when "Brand Portfolio" or "Portraiture Portfolio" are hovered over.   3) Logo and hamburger menu in tablet and mobile view. Because my logo is circle, it does not seem to sit to well in tablet or mobile view. I've used some CSS to move the hamburger menu more to the right, but I'm open to suggestions here on how to improve the look. Could I hide the logo in these views? could I specify a different logo for these views?   Thanks in advance