Urgently need an advanced web developer to work on existing Joomla website

General information for the website: Lottery based website offered to registered users built on Joomla
Kind of development: Customization of existing website
Description of requirements/features: Do you have a passion for web development? Can you deliver a solution under tight deadlines?

I currently have an existing Joomla based website (with a landing page) that offers lottery type functionality to only registered users.
The lottery functionality is carried out by the use of this Joomla extension: http://extensions.joomla.org/extension/raffle-factory

The successful developer will need to be able to edit the extension's php files in order for it to meet my requirements for a more user friendly process that is simple, clear, mobile friendly and easy to navigate. A custom template has already been created and so the successful web developer may choose to work from that in order to tweak the extensions functionality to my requirements.

To meet the above mentioned objectives, I am looking for a good / advanced web developer to develop the following processes for the site:

1. User registration management
2. User Account management
3. Bidding process
4. Winner selection process

Specifically, I want someone with skills & experience in the following areas:

• php, javascript, html5/CSS, jquery
• Experience in Joomla & Joomla Extensions back / front end development a must
• Experience in iOS & Andriod development a plus but not a must
• Experience in implementing third party payment solutions
• Must be able to conceptualize solutions based on written briefs
• Must be able to draw up functional specification and design documents
• Proficient in English language
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