You must have somehow copied the text from a document and it retained some formatting properties.
Delete all your text, and paste it again but this time using Cmd+Shift+V (or Ctrl+Shift+V) so that it’s pasted s text and not as formatted text. Then redo the desired formatting on the desktop view and proceed from there.
To have a different order of elements on devices than on desktop, you don’t have much choices but to use Flexbox. If you move the image for mobile, of course it will affect the desktop. Only what’s defined in the STYLE panel can be changed and defined for each devices without affecting the upper devices.
So, select your Column element, give it Flexbox, now go to devices, and check the “Reverse layout” option.