Thanks Neodeist and the others who gave me some suggestions.
I did what neodeist suggested with a slight variation and I achieved what I wanted to do.
Before I got to step 5, I cleaned up my "old" page . I deleted all the buttons, colors, icons, etc. I only left the List with the layers.
I then continued with step 5 -6-7-
Then I opened the new site with the new theme , added a page with only the Header and then pasted the layers.

So far so good, it seems eveything in working
I'll keep you posted if anything doesn't work.

Thanks again