Overwrite NginX config for subdirectory - nginx

Question

I'd like to install a software in a subdirectory of an NginX Vhost.
Currently I've got:
server {
server_name www.website.com;
root /var/www/website.com/www.website.com/;
gzip_static on;
access_log /var/log/nginx/website.com_access.log;
error_log /var/log/nginx/website.com_error.log;
location = /favicon.ico {
log_not_found off;
access_log off;
}
location = /robots.txt {
allow all;
log_not_found off;
access_log off;
}
location ~* \.(txt|log)$ {
allow 192.168.0.0/16;
deny all;
}
location ~ \..*/.*\.php$ {
return 403;
}
location ~ ^/sites/.*/private/ {
return 403;
}
location ~ (^|/)\. {
return 403;
}
location / {
try_files $uri #rewrite;
}
location #rewrite {
rewrite ^ /index.php;
}
location ~ \.php$ {
fastcgi_split_path_info ^(.+\.php)(/.+)$;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $request_filename;
fastcgi_read_timeout 150;
fastcgi_intercept_errors on;
fastcgi_pass unix:/var/run/php5-fpm.sock;
}
location ~ ^/sites/.*/files/styles/ {
try_files $uri #rewrite;
}
location ~* \.(js|css|png|jpg|jpeg|gif|ico)$ {
expires max;
log_not_found off;
}
}
Now for the subdirectory I tried:
location /mseiten/ {
try_files $uri $uri/ /mseiten/index.php?q=$request_uri;
allow all;
root /var/www/website.com/www.website.com;
}
But all I'm seeing is a 403 if I try to access /mseiten/ in my browser (it should direct me to my installation wizard). I've uncommented all rules that return 403; but with the same results.
Would it be possible to setup sth. like a clean slate for a sub directory?