When I'm trying to visualize a field, on the X axis, which has more then one word, then Kibana split every word into one, for example, bar.
Why is that?
That's actually Elasticsearch analysing things.
You need to set the field to not analysed, have a read of https://www.elastic.co/guide/en/elasticsearch/guide/current/mapping-analysis.html
Aha.
Can I just change this in the default template of logstash?
Or do I need to create a new one?
I suggest you make a copy of the stock Logstash template and configure your elasticsearch output to use your template file instead.