I learnt to ride one last year, 20 inch wheel Is for the beginner and it’s where I started. I rode it every day for about 1 hour and I was riding along unaided happily after a few weeks.
If your committed you can do it in 1-2 weeks,
Look on you tube for tips, I did and picked it up a lot quicker, great fun but you will get strange looks and pointed at like your a freak!
You could look for a local club, that way you’ll learn quicker, there is a local club near me but I never went along.
Good luck and welcome to the circus