Posts at the root level

I would like to publish my posts at the root level.

According to the instructions here:

I saved inside config.yaml the following code:
/: /:title/

but it does not work.
Should I modify something more?
The hugo theme that I am using is multi language, in this case should I do something different?

  posts: /:title/

I tested this, but it does not work neither.
Nothing changes.
It could be because the site is multi language?

I use
“/” = “/:filename/”
in Hugo toml config file because all my posts are at the root level and it works.

Do you use the default toml file of Hugo or the file within your theme?

I use the file config.yaml

if I write there
posts: /:filename/
and I move the article from the folder "pos"t to the content “folder” then it just disappear from the public website.

Apart from the config.yaml file, should I modify something else? if it is relevant I am using a multi language template