I’ve recently been having trouble with my Macintosh and I spent a couple of hours today online with Apple support. During the phone call they asked me to do several things when restarting my computer, things like checking diagnostics, safe booting, Internet recovery, and reinstalling the operating system. A lot of these are covered by keyboard shortcuts you restart your computer.
I do not use my Macintosh for online training, but I was using it the other day and I was surprised to have notifications appearing while I was training. I found that you can turn off the notifications easily in the Notification area (Do Not Disturb), or you can automate the Do Not Disturb to activate at a specific time of the day.