I mean with the webhoster.
The main website is located in the public_html and the subdomains are like this in directory: public_html/subdomainname.com.
In the main .htaccess (which is locatad in public_html) are the rules for the subdomains written like this to work correct:
#RULE:,subdomainname.com,/subdomainname.com
RewriteCond %{HTTP_HOST} ^www.subdomainname$
RewriteCond %{REQUEST_URI} !^/subdomainname.com/
Maybe I can send you a pm for the website.
Thanks Frederick Townes!