bad gateway when trying to build the flarum

Question

get error bad gateway when trying to build flarum forum website

i am a learner at building personal website ,and i learn about nginx and just uploading my website ,but i have some trouble at building the flarum forum site； i have follow several instruction and install the mysql composer and php

and i install the flarum and write the config blow

server {
    listen 80;
    listen [::]:80;
    root /var/www/flarum/public;
    index index.php index.html index.htm;
    server_name example.com;

    location ~ \.php$ {
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/run/php/php7.4-fpm.sock;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    }

    location ~ /\. {
        deny all;
    }


    location = /favicon.ico {
        log_not_found off;
        access_log off;
    }

    location = /robots.txt {
        log_not_found off;
        access_log off;
      access_log off;
    }

    location = /robots.txt {
        log_not_found off;
        access_log off;
        allow all;
    }


}

there is some trouble with the flarum and i get the error bad gateway