I’ve been using Cubase since '92 on an Atari. A lot of the current MIDI editors/tools existed then. When the audio version came out I’d had been doing non-linear recording on the Synclavier system so that helped.
Eventually more powerful computers allowed better VSTi and 3rd party plugins and things got more complex.
Where I’m going with this is that I built my knowledge over a long period of time, step by step. I skipped several versions before 7 so I had some new features to catch up on there.
Here would be my advice to some one totally new to Cubase. There’s so much information involved, you can’t take it in and retain what you’ve read/watched in marathon study sessions. The good news is that you probably don’t need many of the functions in Cubase. So why start off learning about things you don’t even know whether you need?
Pick a composition or song you know well. Start getting it into Cubase the fastest way you can. Don’t get tangled up in the details just yet. Learn how to copy parts, transpose parts, delete notes, correct notes, size notes, quantize.
Next, understand the Audio pool, where your files are disk. How to delete audio you don’t need. How to back up and archive.
Learn how to trim your audio parts to get rid of unwanted noise. A few functions in the audio editor will be handy…silence, fade in or out. Cut pieces of audio for simple time correction. Bounce your edits to new files.
Get a handle on the mixer. Setting up send effects, inserts.
Finally, learn how to create mixdown files.
As you’re doing this song, look up the functions you need in the PDFs but don’t get bogged down. Poke around, see if you can figure out what you’re trying do. Make this a song/performance you don’t care about screwing up in some way or losing. Do incremental saves so you can go back a version or have as backup.
Only worry about learning the things you need for this song. You don’t have to know every possible function of Cubase to create a piece of music. You’ll never remember the info you read then don’t use.
You’ll learn more and more quickly with this approach than watching hours of videos. Cubase is a complex program but you can get up and running pretty quickly. But it’ll take years to fully explore.