Thanks for your answer, I really missed some information above the chapter “Redirects”.
I tried to create page structure like this:
So I made this folder structure:
But I didn’t want to make separate page on site for the chapter “Fractions”. When user cliks on “Fractions” it has to redirect to the “Fractions\Theory”. So I wrote the rule for routing in the header of the file “Tutorial/01.algebra/01.fractions/default.md”
It worked, but another problem appeared. I suddenly found that the page “/tutorial/algebra/fractions/theory” opens on the link “/tutorial/algebra/fractions/theory/theory”, and the page “/tutorial/algebra/fractions/practice” opens by the link “/tutorial/algebra/fractions/theory/practice”. I was really surprised, because I wrote the rule for routions only for one page. After that happened I tried to found the rule for redirect I wrote redirect in the file default.md in the folder “Fractions”, in the file site.yaml and system.yaml, but redirect didn’t work. Now I understand, that my mistake was that I wrote redirect like this (I copied this example from documentation):
But correct rule for redirect is this: