Hi @sisir,
Thanks for checking out the tutorial first.
Turning Cloudflare SSL off, but having an HTTP to HTTPS redirect on your server will cause a loop, Cloudflare is trying to force it to HTTP and your server to HTTPS.
If you already have a valid certificate on your server, you should set that to Full (strict) which will then use Cloudflare’s SSL between the visitor and Cloudflare and then yours between Cloudflare and the server.