nginx: run rails/passenger and wordpress with subfolder permalinks - ruby-on-rails

Question

I need help with my nginx configuration.
I want to run a rails app and a Wordpress blog under the same domain.
Wordpress should be available under a subfolder/path.
Both are already up and running, but I cannot access blog posts.
Here is my current configuration:
server {
listen 80;
listen [::]:80 ipv6only=on;
server_name my-secret-host.com;
passenger_enabled on;
passenger_min_instances 1;
rails_env production;
root /var/www/rails-app/current/public;
# Wordpress
location /news {
alias /var/www/wordpress/;
index index.php ;
try_files $uri $uri/ /index.php;
location ~ \.php$ {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/run/php/php7.0-fpm.sock;
fastcgi_param SCRIPT_FILENAME $request_filename;
}
}
# redirect server error pages to the static page /50x.html
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root html;
}
I tried a lot.
With this variation the Rails app works as expected. Wordpress is also up and running, the admin area and the index page (/) are available.
But if I call a permalink to a post like http://my-secret-host.com/news/2017/10/permalink-test-post/ the rails app responds with an error.
Maybe the solution is stupid and simple, but all my attempts ended in other problems and errors.
Moving the rails config into a location / block didn't change anything.
With disabled rails configuration I get another error, the path to index.php is not properly configured.
[error] 7705#7705: *7 open() "/usr/share/nginx/html/index.php" failed (2: No such file or directory), client: 87.133.34.209, server: my-host.com, request: "GET /news/2017/10/test234/ HTTP/1.1", host: "my-host.com", referrer: "http://my-host.com/news/"
What you see above is a activated/linked configuration file in nginx/sites-available/.
I unlinked sites-available/default, created my own and didn't change anything in nginx.conf– expect of the rails-passenger include.