Nextcloud files visible in the wordpress media folder

Good evening,
I am trying to synchronize the wordpress media file that is there:
For this I use External Storage and fill the line as follows:
Folder name: mediawordpress
External storage: Local
Authentification: Aucun
Configuration: /var/www/wordpress/wp-content/uploads
Available for: pour les admin

My concern is the following when I add a media wordpress I see it in nexcloud. But I can not add a file in this same folder nextcloud indeed the following message appears:
You do not have permission to send or create files here
Do you have a solution to offer me? Thank you