Getting search request timeout after 60000ms

We are currently using Elasticsearch 6.5 and getting intermittent request timeout for some dashboards. We are querying on approximately 550 GB data (76873087 documents) which is distributed among 3 indices. We have 6 data nodes of 64 GB each and 3 master nodes of 8 GB each.
Each index has 6 shards and 1 replica.
So should we increase the request timeout or decrease the amount of querying data or any other suggestion that you may have to resolve this?

Those are your options, along with: beefing up your servers, optimizing your indices, scaling out, etc. If you can query for less data without negatively impacting your use cases, that's the ideal starting point, I'd say.