Can I remove an already published content from Normal view but still keep it in Admin view?

Yes. To remove a published content element from Normal View simply roll it over and from the blue icon appearing in the top left corner choose More. From the list of additional options choose "Hide from viewers". The hidden content will become greyed. After hiding the content, publish the page and the item will no longer be available in Normal View. When you decide to restore the item in Normal View again, roll it over and from the icon > More select "Show to viewers" and publish the change.