In my experience, it's difficult though possible to achieve a basic level of personal and local communication, by means of regular conversation exclusively. I can find an example of conversation in connection with household activities such as washing and cookery. Household objects and equipment for washing and cleaning provide the basis and stimulus for speech. A mother explains to her child that she puts clothes and stuff in the machine, puts powder and gel in, turns the amchine on. At the end of the wash cycle, the child knows that the clothes and stuff are washed and damp, while the mother can speak to explain the same.
Foreign language learning through conversation exclusively is similar, but more advanced. Two individuals could prepare and cook food while the learner listens to a speaker who speaks of the recipe and cooking method in his or her language. These are two examples of basic topics of conversation where the household items and the ingredients for a recipe as well as cooking equipment serve as stimulus and content for speech instead of a book.
However, I believe that we need to use books, or reading material from a web site as well as recorded speech and transcripts, which help us learn and keep up to date with more topic based language and education subjects.
We can give us much importance as we like to grammar as we find suitable. Personally, I like grammar, but I might be unusual. Grammar studies help us read with more accurate interpretation, and with a knowledge of grammar we write more correctly. Foreign language study with some grammar can help improve our proficiency in English.
The best method to adopt when learning a foreign language is with a balance of time spent with reading interpretation, listening to pre-recorded speech, or occasional film. Ideally, we'd find a person from the other country who could dedicate time such as a half hour each week to conversation in his or her own language. If we wish to achieve fluency in the other language , that might be the best way.