Thank you @tuanphan for your help so far. I've added the code and it has fixed the problem of the image sizes, but it is has removed the shadow around images and is giving me this error message:
error evaluating function `rgb`: color functions take numbers as parameters
And it has changed how our logo appears at the top left of each page. On dark pages, it should appear as a white logo and on light pages it should appear as a black logo, but it is black on all pages now so it is hard to see on our home page and impossible to see on pages with a black background.
home page: https://www.wearerise.co.uk/
other page where logo should be white: https://www.wearerise.co.uk/adult-health-and-wellbeing
It has also changed the sub menu but I'm not too concerned about that.
Thank you again for your ongoing help