development of a website with payment system

We are looking for developers or development company for development of a website.

Conditions summary:

• The requirements are written in English.
• Website has to have 2 language interfaces – English and Russian
• Website has to be connected to a payment system Stripe.com. Website will have payments online with credit card.
• Website has to exchange data from personal account of users with mail system Mailchimp.
• Website has to have publications with different level of access (user, Silver member, Golden member, Platinum member).
• Website has to have RSS news storage.
• Website has to use some user-friendly CMS like Joomla with WYCIWYG editor of content, so admins could change any part of this site.
• Website has to have adaptive design according to UI.
• All changes in CMS code and every new function must be described and explained with English comments in the code for further development.
• The website must pass without errors:

1. Google speedtest tool https://developers.google.com/speed/pagespeed/insights/
2. 3WC HTML  validation: https://validator.w3.org/
3. 3WC CSS  validation:  http://jigsaw.w3.org/css-validator/

• The payment will be made in 3 steps:

1. Installation of CMS on a test hosting with developed frontend. Publication of all static pages. – 30%
2. Modification of a registration and account according requirements, development of publication feature, event feature, news feature, Mailchimp connection. Uploading to a real hosting – 30%
3. Payment feature, bug fixing – 40%

Please specify time and price of all works according to this steps.
Please show examples of your portfolio websites with payment system implemented.

UX prototypes:  https://goo.gl/y1ys9C

Software Requirements: https://goo.gl/Ltlud9

UI examples
Desktop: https://goo.gl/zCTXks
Mobile:  https://goo.gl/Hhvepk