Does anybody know how to modify the url struct only for the single post page?

When I go to a post page, the url should look like: example.com/xxx/my-post. All other urls (with the exception of the single post pages) should not contain "xxx" in the url.

Customizing the permalink settings would add xxx in front of taxonomies and categories as well, so that wouldn't work for what I need.

Essentially, I want that all "post" and "events" urls co contain an extra "xxx" segment in the structure.