You might want to tell Google your relationship with outbound links on your site. Discover how to qualify outbound links with rel attribute values.| Google for Developers
The spam policies detail the behaviors and tactics that can lead to a page or an entire site being ranked lower or completely omitted from Google Search.| Google for Developers
When a site has duplicate content, Google chooses the canonical URL. Learn more about canonical URLs and how to consolidate duplicate URLs.| Google for Developers