SEO and Page Indexing in Google

I am running my store using opencart 2.0 for the last 3 years. The website url is https://goo.gl/TZII8S
This website is large with over 500K submitted pages to Google, in the last year we have start losing indexing of the pages in Google, right now we have around 20K index pages in Google, which sucks because we depend on organic search for business.
I am looking for someone with vast knowledge in opencart and Indexing to see if they can put a recovery plan to help us with Google indexing.
If there are any professionals with proof history of doing such jobs I am willing to pay money.

Hello,

We are happy to assist you. You can contact us at sales@ost.agency or skype manish.osuniverse

Regards,
Manish

Hi,

I can help.

You can reach me on Skype: cisin.arnold or Email: arnold2@talentsfromindia.com so that we can discuss this further.

Arnold

Hi there,

We should be able to help with this, would you be able to drop us an email to get an estimate?
info@antropy.co.uk

Kind regards,
Alex
www.antropy.co.uk