Adjusting page of theme

Bought a commercial theme and loaded all demo files.
How can I make a new page, based on a ‘theme page’ maintaining some of its features while adjusting some other features and at the same time keep the theme page as well in its original state.

I thought: “well I just adjust the name of the page, the original page will exist under its original name and I will adjust that page (using visual composer) under its new name (in otters words: editing just a copy). But apparently wrongly thought so: the original page disappears.

Does this have to do with the page address?
If yes, I probably have to adjust the address for the new page, but how, can’t edit the specific permalink)

If not, what should I do instead?
(actually it is a question of: how to copy a certain page and edit and save it under a new name)

Probably very basic, but lost it at the moment…

txs