DMCA removal notice from Google! When / Avoid?

When does the Google DMCA removal notice apply on the website?
What content can cause a warning from Google?
Will I receive a warning if I add a download link to my content? Upload link from the center?

My site is about the introduction of software / graphic file along with photos and download links (external link). But I have notice of DMCA Takedown.

How to prevent Google from enforcing copyright laws?