[THEME] Change list page

Hello, I call you because I have a question and I would like to know if it is achievable.

Here I already own my own cloud theme and I would like to apply it to owncloud. Currently I succeeded for the login page, but I would like to edit this page: /owncloud/index.php/apps/files/ Is this possible?
If this is not possible, is it possible to recover some function of owncloud and inject them into my own design?

Thanks for your support.