Advice on nodes replicas and shards

I have this error in kibana Courier Fetch: 37 of 245 shards failed. even 5 or 6 times at one, after some research I have found that could be due to the number of replicas.
So I run the cluster health and this is the result

{ "cluster_name": "elasticsearch", "status": "yellow", "timed_out": false, "number_of_nodes": 1, "number_of_data_nodes": 1, "active_primary_shards": 316, "active_shards": 316, "relocating_shards": 0, "initializing_shards": 0, "unassigned_shards": 316, "delayed_unassigned_shards": 0, "number_of_pending_tasks": 0, "number_of_in_flight_fetch": 0, "task_max_waiting_in_queue_millis": 0, "active_shards_percent_as_number": 50, "indices": { "log-2015.12.20": { "status": "yellow", "number_of_shards": 5, "number_of_replicas": 1, "active_primary_shards": 5, "active_shards": 5, "relocating_shards": 0, "initializing_shards": 0, "unassigned_shards": 5 }, "log-2015.12.21": { "status": "yellow", "number_of_shards": 5, "number_of_replicas": 1, "active_primary_shards": 5, "active_shards": 5, "relocating_shards": 0, "initializing_shards": 0, "unassigned_shards": 5 }, ... }

And is always like this for all my indices log-* until now log-2016.01.26. I don't know what could be the best solution for me. Should I add another node on another server?

As you have a single node, Elasticsearch will not be able to assign the replicas, which means the index state will be yellow. You can change this through update index settings API. How much memory and heap space do you have for your node?