I can suggest a couple of ideas. You could look around at the library or local college where they may run a variety of short courses on different levels , so you could just start with a basic course on use, and then they sometimes do a more advanced course to do more complicated things.
But the best idea I think is as I used to call it "sit along a Nellie" When I had new staff joining my department, whilst they would be given written and spoken instructions for their work, the best thing I would do is to put them next to the most efficient and knowledgeable worker. If you knew that they were the best workers and understood the system well enough to also do shortcuts , then the newcomer learnt the best ideas from the best. That way they become competent very quickly, and whilst you may be obliged to follow the precise rules of a job, "Nellie" will have sussed out all the best ways to do things, how to avoid tedious ways and how to do a job quickly and efficiently. So you then usually end up with the new staff being quickly brought up to speed. So I suggest you look about your friends and see who seems to be very up to date and uses their phone easily and confidently and then ask for their help. Also see where most people have bought their phones locally. Here, our local Tesco has a good selection and a member of staff who is not at all pushy and listens to what you want from your phone and directs you accordingly. I was pleased with the help I got and of course, as I said , nicely of course, I lived locally so could easily come back if there were any problems!! Also you might ask friends to show you on their phone how to do various things and see if it is easy for you to use. I am a touch typist and bought a keyboard for my laptop as both the phone and laptop used to annoy me so much as I could type faster and without hitting wrong keys with the annoying littlescreen. Good luck