You may want to read the FAQ on cross-communication: https://www.reddit.com/r/AskHistorians/wiki/language#wiki_cross-cultural_communication_and_lingua_francas
This very question was asked 3 days ago
https://www.reddit.com/r/AskHistorians/comments/7xodmv/how_did_explorers_communicate_with_natives_that/
There, you can find a reference to a FAQ with the answers you need.