I offer free installation for this extension
You must have set up your Google Review Merchant account for use of this extension. ( only available for few countries)
How it works
Customers who’ve made a purchase on your site are presented with an option to opt-in to receive an email requesting feedback from Google about their experience with your store. If the customer opts-in, they may receive an email after their order has arrived. The collected ratings are then displayed on your optional Google Customer Reviews badge, appear in your Merchant Center dashboard, and are used for seller ratings.
The Google Customer Reviews program has 4 main features:
Google Customer Reviews opt-in: An offer that appears to all customers after checkout. Users who opt-in may receive an email from Google Customer Reviews asking them to rate their experience with your store.
Google Customer Reviews badge: A badge on your site that helps users easily identify your site with the Google brand. The badge displays the seller rating score of 1-5 stars and can be placed on any page on your site.
Google Customer Reviews survey: The survey is an optional, brief questionnaire that enables customers to rate their purchase experiences with your site.
Seller ratings: An aggregate score that appears on Search ads and Shopping ads, as well on Google Customer Reviews badges. Learn more
How to get started
If you're logged in as an Admin user, you can enable Google Customer Reviews in the Merchant Center programs section, found under the 3-dot icon in your Merchant Center account. After you select Enable, follow the steps to add the Google Customer Reviews program to your site. Learn more
Once you have enabled your account and completed the enrollment steps, stats about your opt-in metrics, surveys, and seller rating will be available in your Google Customer Reviews dashboard in Merchant Center.
And you should be able to upload and edit file on server . This extension use configurations that are edited in file in system/config . Not from admin .
I have same extension that can be set up from admin HERE
This is how that file looks. Take a look and if you know what to put in this file than buy this extension.
$_['google_merchant_id'] = '000000'; //Your Google Certified Shops ID.
$_['order_estimated_delivery_time'] = '1';//in days. Don't leave empty!!!! Use 0 instead. The estimated days for which you expect delivery of the order to the customer. If the order contains multiple items, select the latest delivery date