I heard from one of my classmates that another classmate of mine was studying traditional Chinese medicine and h. He said that one day’s learning when you were young is worth more than your ten days learning when you are old.

It makes sense the way you wrote it, but I think adding "worth" makes it sound more natural.

But the problem is that when you are young, you will probably don’t want to learn.

What else can I say next?

I think this makes sense without the "next"

I heard from one of my classmates that another classmate of mine wais studying traditional Chinese medicine and h. That classmate said that one day’s of learning when you weare young is more than your ten days learning when you are old.

But the problem is that when you are young, you will probably don’t want to learn.

When you want to learn something atin your old age, your memory is too bad to remember it.