Please help me with Discourse installation i am a super newbie

The page shown at that domain looks like a default page provided by some other web server software (Apache, I think) which might mean you’ve created your VPS using a LAMP image.

When you created the VPS, did you choose an option that mentioned anything about hosting websites? If so, it may be worth recreating the VPS with a different image, a base Ubuntu image which doesn’t include any software for web hosting.