A new InDesign document should be entirely blank. No content on any page. Only one layer called "Layer 1".
The fact that you have page numbers and lines showing up on new pages, and that there are two named layers in your document tells me that you must be using some kind of template document made by another designer.
Actually your issue has nothing to do with page numbering. The reason why page numbers and lines are appearing on new pages is because the designer of the document you are using intentionally placed those objects on a Master Page.
The master pages are shown above the ordinary pages in the Pages panel.
Any object you place on a master will appear (as locked objects) on every page which has that master applied. By default, a new page in InDesign has the first of the masters applied, but you can drag and drop the wanted master (or the special master [None]) on a page to change it.
Masters are mainly used for (as you might have guessed) design elements which must appear in the same place on many pages. Like page numbers, lines, background colors, logo in the corner etc.
If you want to remove the page numbers and lines on every page (which has the master applied), simply enter the master by double-clicking it, select the unwanted objects and delete them.
Read about Master Pages in Adobe's online manual
The two layers you mention must be created by the designer of the template. They have no special meaning and can be moved, duplicated, renamed and deleted as you wish. You can add your own layers.
If you want page numbers and lines on most pages, but just want an image to cover them occasionally, you can create a layer on top of the other layers and place your image there.
If you later change your mind, you can just move that layer below the other layers and then the page numbers from the master page is on top again.
Read about Layers in Adobe's online manual
If you don't want any design elements at all - just blank pages, you should just start over with a new blank document at the desired physical size. No need for a template document in that case.