Sorry another question is now my picture for different product become different sizes, please see attached. Kindly advise on how to standardise the picture in single product page?
The problem may occur when you switch between themes in Appearance -> Themes is that widgets may lose their positions. It is a WordPress behavior and we are not able to fix this in our theme scope. Now, you need to go to Appearance -> Widgets and move all widgets to appropriate positions.
As a workaround, you can backup your widgets configurations using this plugin https://wordpress.org/plugins/widget-importer-exporter/
As for images sizes, so you can manage them via Dashboard -> Appearance -> Customize -> WooCommerce -> Product images.
Thank you for the prompt reply and precise answers. Sorry now I experience another problem,
All my uploaded pictures become square with coloured boulders forming top and bottom of the pictures, I have uploaded them for about us and contact us page.