How to make child posts to a post with navigation?

Question

WordPress

Need to get something like this

-post1
--post1_1
--post1_2
--post1_3
-post2
--post2_1
--post2_2
--post2_3

The category will display a list of parent posts. By clicking on the link, the content of the original post with pagination by children will be visible, where 1 is the original post, 2,3,4 are the children. The template is the same (single.php).
And it is desirable that the content of child posts in the admin panel be input (header) + wyssiwyg (content) fields in the original.
Perhaps there are some ready-made solutions or something that can be completed fairly quickly.
Thanks in advance!