Cubase is a deep program with a long learning curve. Although the .pdf manuals are indispensable for comprehensive coverage of features, it’s hard to get the big picture, and hard to become efficiently hands-on merely by hours of reading.
MacProVideo has published a large range of Cubase instructional videos ranging from entry-level instruction to demonstrations of more complicated features. They’re reasonably priced, thorough and clear. Although I’ve read and re-read (at least parts of) the .pdf manuals over the years, I think the fundamental information is more easily understood on screen. Check out the videos at Cubase Course Library : macProVideo.com - there are a few samples which may help you decide.
Another commercial video tutorial series, though not as comprehensive is available from Groove 3 - Groove3.com
Also check out any videos by Greg Ondo on YouTube.
Good luck.