Joomla Fix and Upgrade

Closed - This job posting has been filled and work has been completed.

Job Description

My business website has been created with Joomla.
The person that created it does not know how to fix it.
What has happened is that if you click on the website, for some people the website is fine, for others it automatically redirects to a gambling site. I think this is a virus but not sure.
What I want to do is remove this virus and upgrade Joomla to the latest version.
I am limited by budget.
The website is
Thank you.