I think i have done everything correctly. However, the error The index pattern does not contain any of the following compatible field types: geo_point is still there.
***** My filter part was like that: (in logstsh conf file) *****
filter {
csv {
separator => ","
  mutate {
  add_field => [ "[geoip][coordinates]", "%{[geoip][longitude]}" ]
  add_field => [ "[geoip][coordinates]", "%{[geoip][latitude]}"  ]
}
mutate {
  convert => [ "[geoip][coordinates]", "float"]
}
***** My template was like that: *****
PUT _template/indexname
{
     "index_patterns": "indexname*",
     "settings": {
     "number_of_shards": 1
},
       "mappings": {
       "_source": {
       "enabled": false
},
      "properties": {
        "geoip":{
           "properties":{
              "coordinates":{
                "type": "geo_point"
     }
    }
   }
  }
 }
}