Wooow, it's working. THANKS! 
I don't understand why should I determine that I want highlight on text in the search level (and not at highlight section)?
Another question, let's say my document looks like this:
{ 
  "type": "tweet",
  "fields": {
         "user" : "jack",
         "message" : "I'm jack",
         "comment" : "my first tweet"
         }
}
Can I search on fields.* instead of  specific fields, like: {fields: "comment, message", query: "your query"}?
I understand that on _all it's not working, but I see in elasticsearch documentation that I can use wildcard, they use the follow example:
{
    "query_string" : {
        "fields" : ["city.*"],
        "query" : "this AND that OR thus",
        "use_dis_max" : true
    }
}
For me it failed with SearchPhaseExecutionException 
Any suggestion?
Thanks,
Effi