Hi Amran,
you can change the tilemap.options.maxZoom setting in the kibana.yml file to get more zoom levels. There is more information in the docs about the tilemap settings (https://www.elastic.co/guide/en/kibana/current/kibana-server-properties.html#tilemap-settings).
In the linked github ticket above, other people have inquired about using OSM tiles, so you can read up there. That said, I don't think OSM terms of service allow that, so please be careful.