If you are like me, with all the constant changes, it is easy to forget the functionality available, particularly if you do not use it very often.
On Cult of Mac, they had an article "All you need to know about Slide Over, Split View in iOS 11”
Cult of Mac Link
I have personally found two resources quite useful. The first is ScreencastsOnline which is operated by Don McAllister and offers a subscription model although some videos are free to watch.
Another that is free and has had many useful videos is MacMost. From the site "MacMost is a free website with video tutorials for Apple Mac, iPhone and iPad users. Visit here daily for new tutorials, sign up for the free weekly newsletter, check out some Mac tips, and ask questions in the forum. New to the Mac? Check out the Beginner’s Guide to the Mac."
Of course if you prefer to have assistance in resolving any issues with your computer or need to solve some requirement with your software or hardware, I am able to assist with personal service at reasonable rates. The initial assessment of your requirements is free, unlike many trades that charge exorbitant fees just to arrive at your door.