Hi, thanks for posting your question.
If no changes are made to the markup, you can switch out of Page Builder and back in without losing the page formatting and structure. If page revisions aren’t available, you might consider chatting to your hosts about a site backup to a date prior to the changes made.
Given the size of the page though, it might be quicker to rebuild. You can go to Pages > Add New and create a sandbox/working page. Once your layout is ready, go to the destination page and in Page Builder click Layouts > Clone: Pages. You can clone the layout from your sandbox/working page into the destination page. That way you can copy content without disturbing the page as it is now.
Yes, iI have created again after posting the question. Thank you for your support.
Thanks for the update and your understanding. Apologies for the hassle. Please, let us know if any queries arise in the future.
Cheers
Andrew