For example, when the British came to North America, how could they have talked to the Natives and learned their language(s)? How about when the Spaniards/Portuguese reached South America? And since they couldn't communicate properly immediately, how did they react to each other upon first contact?
hi! this is one of those questions that could have almost infinite answers to cover every scenario, so new input is more than welcome. meanwhile, there's a section on the FAQ* with previous discussions - see particularly subsections How did people speaking different languages communicate? and How did colonialists talk with indigenous people?
Cross-cultural communication and lingua francas
*see the link on the sidebar or the wiki tab