Permalinks not working

Hello, dear Hugoers!
I have some problem with Permalinks.
Here is my config.yaml:

permalinks:
  documentation: "/:year/:month/:title/"

However, the URLs does not follow this schema. They stayed with the old content-based links.
My website is here:

Thanks a lot for the help.

You’re configuring a permalink that requires your content to have date in its front matter… but most of your content pages under your documentation section don’t have this.

Add date to all of them, and your permalink should work.

Thanks a lot, let me try.
Another quick question: is it possible to have articles using normal URLs (content based), but configure aliases based on the date for all articles?
For instance:
This article is served at its normal URL: www.example.com/documentation/topic1/

My article
=======

Blabla 

Permalink for this article: www.example.com/2019/02/topic1

The idea is that each article contains a link to its permalink location, so the user can link it safely.
My website is aimed at documentation, so content-based links are OK and look nice.
However, site reorganization happens often and breaks external links.
I looked for an “alias” configuration setting for config.yaml, but couldn’t find it.

Please read the docs for information, not just the config options: https://gohugo.io/content-management/urls/#aliases