How many nodes do you have in your cluster?
We register 300-500 entries by the instance on average. Again, user write/and requests to elasticsearch is around 250-300 by the instance.
I don't understand what that means. How many indices do you have? How many documents are you indexing per second (or hour, or day...)? How many search queries are being submitted per time unit?
System works on 2 replicas and 5 shards.
Why do you have 2 replicas?