Grand-Motion Wedding Slideshow | Beautiful Love Story

I downloaded a comp of Grand-Motion Wedding Slideshow | Beautiful Love Story which only has 12 scenes but I should add more. The fact is that I don’t understand anything anymore because when adding comps, obviously duplicating the old ones, it also takes away and replaces the old files… help me please

This happens because the precomposition in the project works as a folder on the computer, and all places where it is used work as a shortcut to this folder.
To make the precomposition unique, right-click on the precomposition and select “reveal layer source in project” to find the primary coposition in the project

Then duplicate it (Ctl+D or Command+D)

Now this precomposition is unique, you can replace the old precomposition with the new one in your project (drag and drop it on the old precomposition with the “Alt” key held down)

Now the precomposition in the project is unique and will not change when you change the previous precomposition.

But keep in mind that all precompositions within the new precomposition must be updated in the same way.
If the structure of еру project you are using is very complex or you find it difficult to do what I wrote, I would advise you to simply duplicate your project in a folder and work in several projects separately