I often have people telling me that they are good at understanding written or spoken French, Spanish or German, but really struggle replying and they wonder why. I think there is a good explanation for this.
Firstly, formulating a response requires much more than just putting a few sentences together. Putting the sentences together is the tip of the iceberg. For these to be intelligible, they have to make sense to the listener. This in turn means that the learner has to have understood what was said in the first place. Therefore, the language learner's brain is already in overdrive before they utter a single word.
Also, learners often question whether they have correctly understood what was said to them. My advice here is to assume you have. And if you haven't, your response is not likely to trigger a world war, so don't worry about it too much. It's better to communicate something than to be turned to stone by self-doubt. Or, take a step back and check you have understood. It's very easy to ask someone to repeat or rephrase something; we do it all the time in our own language in noisy environments and no-one thinks anything of it.
Furthermore, it may be that the person you are talking to does not require a complete answer from you - they may be looking at you simply for a signal to show that you are following (to a greater or lesser degree) what they are saying. It is very hard for a speaker to continue if he or she does not know whether the listener is engaged. So, in this case, you just need a couple of set phrases such as 'ah bon', 'bien sûr', 'ah sí' or 'claro'. The speaker is then reassured that you are not stuck in the quicksand of their language and they'll carry on speaking (which gives you a reprieve!) The good news is that there is every possibility that your mind will catch up with the general flow of the conversation and you'll then be able to participate.
And so now it's your time to talk. Learners often think this is the hard bit, but actually getting to the stage where you have understood enough of the conversation to have thought of a contribution is harder still in my mind. Now you are holding the conch, don't get caught up in this momentous occasion. Instead, just say something and pass the conch on. You don't have to say anything complicated or impressive and people will be thrilled you are communicating with them in their language instead of making them speak yours. And of course, it's only a conversation when there is an exchange between two people, so you are right to give the others another opportunity to speak: after all, you don't want to be accused of hogging the conversation!
The third stage in this process, after having listened and understood and then replied, is to metaphorically pat yourself on the back but also remind yourself that what you have just done was not that hard. The hard part is pushing yourself to do it in the first place instead of taking the easy way out and saying, 'Parlez-vous anglais?' And you'll find that the next time gets easier, and the time after that even more so. Actually, I would argue here that your ability to converse hasn't got any easier, but your confidence has increased massively... because you've done the hardest part, succeeded and maintained a conversation!
The above partly explains why people enjoy our conversation groups. The vocabulary emailed out beforehand means that people are familiar with the language being used and the crib sheets offer enough support to get you to the crucial stage where you are ready to join in the conversation without the brain already overdrive. Everyone is so relaxed that confidence soars and then the conversations go hors piste. And that's when the authentic conversations and fun really starts...