I create a mutisite with subdirectories because subdomain

I create a mutisite with subdirectories because subdomain impossible to work. triing with Jack and week-end dont find.
I think about domain mapping
1. configure the plugin : ok
2. create manually in plesk cause impossible to it in a dynamic way the sub domain "aaaa" : ok
3. Try to domain map "easy1er.fr/bbbb" to "aaaa.easy1er.fr"
4. Tuto tell to config Dns but can't enter "easy1er.fr/bbbb" in CNAME config or A config can't put "easy1er.fr/bbbb"
(screenshot)
QUESTION : How can I do to map a subdirectory to a subdomain ?
Impossible to have dynamic subdomain, Impssible to have domain mapping ?? Wheres the pro point of vue
(I contact WPMU, PLESK from Parallel and Wordpress.org, no solution in One month : Crasy !)