Similar to a previous commenter, I’m 18 years and 6 months old and I got my class 2 a couple of months ago. I drive rigids everyday and, truly, I find it considerably easier than driving a car! Some people do just take to driving very quickly and ‘effortlessly’ and you might not be one of those people. It definitely sounds like your instructor is an absolute zeebee (as they say) and maybe it would be worth trying to go on to do training with another provider.
Any questions please feel free to PM me; I know what it’s like starting at such a young age! 