So, after endless fiddling, researching and reading, I have found the solution. If anyone has the same problem with nginx and pretty urls, here is my solution:
in an nginx.conf-file:
location / {
:
try_files $uri $uri/ @rewrite;
:
}
location @rewrite {
rewrite ^/(.*)$ /index.php/$1 last;
}
Ergo: The note in the admin interface
location /docs/ {
try_files $uri $uri/ /docs/index.php?$query_string;
}
is probably not correct.