Why classes studying before arrays?

Because arrays are objects of the Array class :)

because array is a class. so it has properties and methods which you cannot refere as such if you don't know what a class is. welcome to OOP ☺

why not?

agree with James ;))))

oh, thanks. I asked this because we learned arrays before classes in our university

That's just how Sololearn teach. There's not much we can do about it unfortunately.