A lot of English speaking people don't understand English either, so anyone who doesn't is in good company. The problems with communication may be overcome gradually, as people learn that different languages often just mean the same thought in different words, as people find access to so many language versions on the net, that would not have been believed a few years ago. Gradually working to the ideas that are unique to a language. Something like hearing a language that may seem impossible to understand, and when told what has been said by a translator, there suddenly is no surprise, that the talk was something, that anyone would be likely to say.

Nice mini-study on different languages , in general. Thank you very much. You've made psychological description of dialogue. When two persons talk in different languages, the talk take place in given and well known circumstances. All senses are engaged and work all the time. Plus imagination, of course. I think we all have an instinct of understanding (or being understood). That's why we can anticipate what our chat-partner is talking about. It is very, very interesting phenomenon.
On the other side we are very "all is clear"-thirsty. So, we prefer to talk in the same language - in Middle Ages in Latin, in 18th and 19th century in French and now English has its time.