Don’t confuse a foreign language with one which we do not know sufficiently well. There are times when we cannot understand someone who speaks our native language. We know all of the words, but we still cannot understand what the person is saying.
A foreign language is basically the same kind of language as the one which we speak. The only difference is that we do not understand any of the words that we hear. A true foreign language differs from a language that we simply do not speak in one very elementary way.
We understand those words and can understand the topic – food, travel, sports, shopping, prices, the weather, etc. That is all, however. We cannot move beyond the overall topic that is being discussed. Don’t fear, though – if you understand the general topic of discussion, then that means that you can identify the language that is being spoken – Spanish, French, Italian, etc. This means that this is not a completely foreign language to you. You simply do not understand it sufficiently well.
The next thing is this: A language will turn from an incomprehensible into an understandable one only when you not only recognise the words that are spoken, but also understand the point to what is being said.
Sadly, some people who want to communicate in a foreign language in a comprehensible way must first learn to do so in their own language. You have to remember a few things here. If people talk to one another they only use words which the others will understand, and they use those words so that everyone understands the point to what is being said.