Nginx 12 FastCGI sent in stderr Primary script unknown

I am struggling for two days with my nginx configuration. I read a lot but could not find the right question.

I got this from the error log:

2018/08/30 09:36:29 [error] 1525#1525: *12 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 127.0.0.1, server: admin.local, request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/run/php/php7.2-fpm.sock:", host: "admin.local"

The thing is, yesterday i was able to load admin.local in my browser. Only fault was i got "File not found." if i klicked a link. (could not go deeper than /admin.local/)
Now I got "File not found" on the landing page. I haven't changed anything.

my system:
Linux Mint 18
PHP 7.2.9-1+ubuntu16.04.1+deb.sury.org+1
nginx version: nginx/1.14.0

location of my index.php:

lrwxrwxrwx 1 www-data www-data   40 Aug 29 13:49 admin -> /home/me/projekte/admin/public/

My nginx x directory looks like:

.
├── conf.d
│   └── default.conf
├── fastcgi_params
├── koi-utf
├── koi-win
├── mime.types
├── modules -> /usr/lib/nginx/modules
├── nginx.conf
├── scgi_params
├── sites-available
│   └── admin.conf
├── sites-enabled
│   └── admin.conf -> ../sites-available/admin.conf
├── snippets
│   └── fastcgi-php.conf
├── uwsgi_params
└── win-utf

nginx.conf

user  nginx;
worker_processes  1;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;

    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*.conf;
}

admin.conf (/sites-enabled)

server {
    listen 80 default_server;
    listen [::]:80 default_server;

    root /var/www/html/admin;
    index index.php index.html index.htm index.nginx-debian.html;

    server_name admin.local;

    location / {
    try_files $uri $uri/ /index.php$is_args$args;#=404;
    }

    location ~ \.php$ {


        try_files $uri =404;
                fastcgi_read_timeout 864000;
                fastcgi_split_path_info ^(.+\.php)(.*)$;
                fastcgi_index index.php;
                fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
                #fastcgi_param SERVER_NAME $host;
                fastcgi_param PHP_IDE_CONFIG serverName=$server_name;

        include /etc/nginx/fastcgi_params;
        fastcgi_pass unix:/run/php/php7.2-fpm.sock;
    }

    location ~ /\.ht {
        deny all;
    }
}

etc/hosts

127.0.0.1   admin.local

fastcgi_params

fastcgi_param  SCRIPT_FILENAME    $document_root$fastcgi_script_name;
fastcgi_param  QUERY_STRING       $query_string;
fastcgi_param  REQUEST_METHOD     $request_method;
fastcgi_param  CONTENT_TYPE       $content_type;
fastcgi_param  CONTENT_LENGTH     $content_length;

fastcgi_param  SCRIPT_NAME        $fastcgi_script_name;
fastcgi_param  REQUEST_URI        $request_uri;
fastcgi_param  DOCUMENT_URI       $document_uri;
fastcgi_param  DOCUMENT_ROOT      $document_root;
fastcgi_param  SERVER_PROTOCOL    $server_protocol;
fastcgi_param  REQUEST_SCHEME     $scheme;
fastcgi_param  HTTPS              $https if_not_empty;

fastcgi_param  GATEWAY_INTERFACE  CGI/1.1;
fastcgi_param  SERVER_SOFTWARE    nginx/$nginx_version;

fastcgi_param  REMOTE_ADDR        $remote_addr;
fastcgi_param  REMOTE_PORT        $remote_port;
fastcgi_param  SERVER_ADDR        $server_addr;
fastcgi_param  SERVER_PORT        $server_port;
fastcgi_param  SERVER_NAME        $server_name;

# PHP only, required if PHP was built with --enable-force-cgi-redirect
fa

stcgi_param  REDIRECT_STATUS    200;