@Jan Dembowski
Nope, that didn't do the trick.
When I add the suggested command line above the location ~ \.php$ I get the error
Restarting nginx: [emerg]: duplicate location "/" in /etc/nginx/sites-enabled/default:41
configuration file /etc/nginx/nginx.conf test failed
After that happened, I tried to implement
try_files $uri $uri/ /index.php;
into location ~ \.php$ itself
I did disable the try_files $uri @wordpress;
part in the code when I tried your code. :)
It resulted into 404 errors when I turn on custom permalinks.
Any other suggestions maybe?