When it comes to effective communication, it does not matter if you speak your mother language or a foreign language. What is most important is the goal you have in mind. What do you actually want to say?
By listening to a lecture or to public speakers, you realize that good speakers can move the audience. Their goal is to keep the audience listening. For them a good event is not only the content itself, but the way how this content is presented.
This effect is same when it comes to speaking effective in a foreign language. Once you eliminate the fear to speak, you are able to communicate. If the other person is willing to listen to you, you can speak. For that process you don't need a high amount of words. However, the number of words you remember in a foreign language will help you to speed up a conversation.
Do you struggle talking in a foreign language? What's your personal survival strategy?