Are there in the world any native speakers of Esperanto? If yes, can they communicate with world or do they've to learn another language?
Yes, there are natives, but all Esperanto natives have multiple native languages. They usually have parents with different native languages who use Esperanto as language of the house. So the Esperanto natives have a mother tongue, a father tongue, a parents tongue and sometimes even a kindergarden tongue.
I know several native Esperanto speakers personally. As far as I know, they are all at least bilingual. Wikipedia has an article about this topic.
Esperanto like a native This excellent video also answers quite a few of your questions. I haven't been learning Esperanto for very long, but I have met quite a few native speakers already. All are - at least - bilingual, because there is no place in the world where you could grow up and only speak Esperanto. The ones I have met speak English, French or German as a second tongue, for example.