Getting PHP 5.3 to work with NGINX

For specific reasons I installed PHP 5.3.5 on an Ubuntu Server 18.04 LTS. At the moment I can't get the php to work when I call it.

I used the following topic to install PHP 5.3

Can I install PHP 5.3.5 on Ubuntu Server 18.04 LTS?

When calling index.php I get a 404 back. Files like html, jpg, txt works fine.

This is my "/etc/nginx/sites-available/default"

server {
    listen   2053;
    server_name  localhost;
    access_log  /var/log/nginx/localhost.access.log;

## Default location
    location / {
        root   /var/www;
        index  index.php;
    }

## Images and static content is treated different
    location ~* ^.+.(jpg|jpeg|gif|css|png|js|ico|xml)$ {
      access_log        off;
      expires           30d;
      root /var/www;
    }

## Parse all .php file in the /var/www directory
    location ~ .php$ {
                try_files $uri =403;
                # Alternatively you can set
                # cgi.fix_pathinfo = false
                # in php.ini
                include /etc/nginx/fastcgi_params;
                keepalive_timeout 0;
                fastcgi_param   SCRIPT_FILENAME  $document_root$fastcgi_script_name;
                fastcgi_pass    127.0.0.1:9001;
    }

## Disable viewing .htaccess & .htpassword
    location ~ /\.ht {
        deny  all;
    }
}
upstream backend {
        server 127.0.0.1:9000;
}

php -v

PHP 5.3.29 (cli) (built: Aug 26 2021 08:30:28)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2014 Zend Technologies

whereis php

php: /usr/local/bin/php /usr/local/lib/php

Is there a way to get this working?

Thank you in advance.