#From these the coastland peoples separated and went into their lands

"Javan's sons and descendants separated and moved to the coastlands and islands"

#coastland peoples

This refers to people who lived along the coast and on the islands.

#their lands

These are the places that the people moved to and lived in. AT: "their homelands."

#every one with its own language

"Each people group spoke its own language" or "The people groups divided themselves according to their languages"