After you duplicate a post it is a draft. First click in the page title and change it. Select the proper category and a featured image if you want one. Then in the RH corner of the top bar click on save as draft.
Edit what you want and save as draft. When you want the page to show on the website select publish. If you make any changes remember to click update.
NOTE: There are lots of websites with info on how to edit wordpress pages. Here is one:
How to change or delete a block:
Click in the section ( block) that you want to change or delete.
The red arrow is where you click to see other a few other block options if for example you want to change the heading block to a paragraph.
The black arrow points to 3 dots which when you click on will open a menu with several options, the bottom option is always delete
To Add an entirely different block:
Click on the blue plus icon which open a menu with many types of blocks. Click on one and it is added to the bottom of the page