How to create a custom page base on URL for WordPress?

How can I achieve the following:

example.com/mycategory/my-first-page

example.com/mycategory/a-random-file-name-page

If the user enters http://example.com/mycategory/*, it will load a standard template page. Inside this page would display a page title depending on the URL e.g. my-first-page will display as “My First Page” with some static contents.

Please advise how should I go about doing that.

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