ubuntu - Nginx downloads 'download' file instead of executing PHP

one text

This is my configuration:

server {
 listen 4343 default_server ssl http2;
 listen [::]:4343 default_server ssl http2 ipv6only=on;
 server_name mail.napegaming.eu;
 root /var/www/roundcube/;
 index index.php index.html index.htm;

 ssl_certificate /etc/letsencrypt/live/mail.napegaming.eu/fullchain.pem;
 ssl_certificate_key /etc/letsencrypt/live/mail.napegaming.eu/privkey.pem;
 include /etc/letsencrypt/options-ssl-nginx.conf;
 ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;

 error_log /var/log/nginx/roundcube.error;
  access_log /var/log/nginx/roundcube.access;

  location / {
    try_files $uri $uri/ /index.php;
  }

  location ~ \.php$ {
   try_files $uri =404;
   fastcgi_pass unix:/run/php/php-fpm/php-fpm.sock;
   fastcgi_index index.php;
    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    include fastcgi_params;
  }

  location ~ /.well-known/acme-challenge {
    allow all;
  }
 location ~ ^/(README|INSTALL|LICENSE|CHANGELOG|UPGRADING)$ {
    deny all;
  }
  location ~ ^/(bin|SQL)/ {
    deny all;
  }
 # A long browser cache lifetime can speed up repeat visits to your page
  location ~* .(jpg|jpeg|gif|png|webp|svg|woff|woff2|ttf|css|js|ico|xml)$ {
       access_log        off;
       log_not_found     off;
       expires           360d;
  }
}

Everything works. When I enter website there is just 403 which is OK but when I enter /installer which should start installation of roundcube webmail it just downloads: 'download' file. When I open it there is code of index.php of roundcube installation folder.

SSL certificates are valid. php-fpm.sock is OK so I don't know where is the problem.