Recommend Best Setting For ElasticSearch Index

Hey Guys, I have recently joined a project which is integrated with elasticsearch to store the JSON Request Response payload for each api call and transformation activities for each api call by a application. We are using default setting with below infra.
Platform: Linux
Ram: 15GB
Disk Space: 600 GB
App. Logging Activities : 4009267 (expected to grow with increase in more user to start using the API).
ElasticSearch Index: 1
"number_of_shards":"5"
"number_of_replicas":"1"
Mapping columns : 17

With these settings, we filled up our file-system within a week which causing loss of data.

  1. What is the best setting at elasticSearch level or more specific at index level should be used to maintain such heavy data.
  2. Data is required to maintain for 90 days, so in this case even if i use delete api query to delete 91st day of data and then reclaim query, it doesn't work or take long long time to process.
  3. If i understand correctly, deleting the index or empty the index is much much faster, hence i am thinking to have multiple indexes creating on weekly basis so that data purging can be achieved much faster. Any thoughts on this?