Why is '"if" directive is not allowed here in /etc/nginx/sites-enabled/vst-install.sh:15' displayed after installing an SSL certificate?

Question

Nginx

Followed the installation instructions: create 2 files with keys, with the domain name and extension (.crt, .key). Edited the nginx site config, gives:

Failed to start a High perfomance web server and a reverse proxy server

I look at the nginx logs, writes that there is an error in a file that I have never touched:

"if" directive is not allowed here in /etc/nginx/sites-enabled/vst-install.sh:15

Where to look for the reason - in nginx conf. or in vst-instakk.sh? I'll throw off both files...
Site config:

server {
  listen 443 ssl;
  ssl_certificate /etc/ssl/premsite.ru.crt;
  ssl_certificate_key /etc/ssl/premsite.ru.key;
  root /var/www/sites/projects/Business/public_html;
  set $php_sock unix:/var/run/php/php7.3-fpm.sock;
  index index.html index.htm index.php;

  server_name premsite.ru;

  location / {
    try_files $uri $uri/ =404;
  }
  location ~* ^.+\.(jpg|jpeg|gif|png|ico|tiff|css|js)$ {
    expires 6M;
    add_header Cache-Control public;
  }
  location ~ \.php$ {
        	include snippets/fastcgi-php.conf;
        	fastcgi_pass $php_sock;
        	fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    }
}

vst-install.sh:

#!/bin/bash
# Vesta installation wrapper
# http://vestacp.com

#
# Currently Supported Operating Systems:
#
#   RHEL 5, 6, 7
#   CentOS 5, 6, 7
#   Debian 7, 8
#   Ubuntu 12.04 - 18.04
#

# Am I root?
if [ "x$(id -u)" != 'x0' ]; then
    echo 'Error: this script can only be executed by root'
    exit 1
fi

# Check admin user account
if [ ! -z "$(grep ^admin: /etc/passwd)" ] && [ -z "$1" ]; then
    echo "Error: user admin exists"
    echo
    echo 'Please remove admin user before proceeding.'
    echo 'If you want to do it automatically run installer with -f option:'
    echo "Example: bash $0 --force"
    exit 1
fi

# Check admin group
if [ ! -z "$(grep ^admin: /etc/group)" ] && [ -z "$1" ]; then
    echo "Error: group admin exists"
    echo
    echo 'Please remove admin group before proceeding.'
    echo 'If you want to do it automatically run installer with -f option:'
    echo "Example: bash $0 --force"
    exit 1
fi

# Detect OS
case $(head -n1 /etc/issue | cut -f 1 -d ' ') in
    Debian)     type="debian" ;;
    Ubuntu)     type="ubuntu" ;;
    Amazon)     type="amazon" ;;
    *)          type="rhel" ;;
esac

# Check wget
if [ -e '/usr/bin/wget' ]; then
    wget http://vestacp.com/pub/vst-install-$type.sh -O vst-install-$type.sh
    if [ "$?" -eq '0' ]; then
        bash vst-install-$type.sh $*
        exit
    else
        echo "Error: vst-install-$type.sh download failed."
        exit 1
    fi
fi

# Check curl
if [ -e '/usr/bin/curl' ]; then
    curl -O http://vestacp.com/pub/vst-install-$type.sh
    if [ "$?" -eq '0' ]; then
        bash vst-install-$type.sh $*
        exit
    else
        echo "Error: vst-install-$type.sh download failed."
        exit 1
    fi
fi

exit

Everything was fine before SSL.

Answer 1

Why did you put this shell file in the nginx sites config folder?
He tries to connect it as a config file, respectively, expects that the syntax in it is like in the nginx config file, and not in the shell file