Without dictionaries, how were languages learned in the past?

Answer 1

The old-fashioned way: immersion! People would come in contact with speakers of a language they did not understand, and would try their best to understand each other.

A newcomer to a place where everybody spoke a common language that he did not understand might listen to conversations in public places, and eventually pick up things like "Hello," "Goodbye," "Thank you," and "Who are you?" Once you are able to use simple phrases, people are likely to point out items or actions and give you the word for it, until you're able to ask more complex questions and communicate more fully. If there's somebody new in your town, you're likely curious and want to communicate with them just as much as they want to communicate with you.

If two groups that speak different languages come in contact with each other, they'll likely start blending their languages to be something like a cross between the two, using some useful grammatical features of one language and some helpful vocabulary from the other until a new language is born from the two, to be spoken by future generations.

This kind of thing is still happening today! Many minority languages do not have dictionaries, so any newcomer must try their best to understand what is being said and to communicate back. Even in languages that have dictionaries, many people learn by immersion, by choice or because they don't have the time or money to learn formally. Language is best learned in community, so find a native speaker and work until you can understand one another! The process is extremely rewarding!