Elastic Search querry

Hi,
I'm new to elastic search and I was trying to make an android app to make some queries from this website using URL queries:

http://search.digikala.com/api/search/

I was trying in my browser every possible syntax that I could come up with in google but nothing worked. the returned Json is always the same results. can anyone help me with this?

to be specific I'm looking forward to search in a string named :EnTitle located in _source object.
thanks in advance.

Very likely someone built their own URL/query parser for the site, so you
would need to ask the operator of that site. The URL structure does not
appear to make that of Elasticsearch.

Ivan