I did not become fluent in five days in Prague. However, I improved tremendously. I am comfortable in Czech. I read, I listen and understand. I can take part in a conversation but stumble here and there. I will post a video of an interview next week if I can.
Yet I feel that my whole fluent in five days experiment was a success. I have acquired a new language. I am not far from fluency. If I had the chance to live in the Czech Republic for a month or two I would certainly be fluent. If I had stayed there a few weeks instead of just four days I would have consolidated my hold on Czech.
As it was I left Prague and did not speak the language for the following month. Not ideal. But it does not matter. I falied to achieve fluency but I succeeded in becoming much more comfortable in Czech. I am now going to try to do the same in Korean.
Ultimately, fluency requires lots of interaction in the language. Once I have built up the base through my reading, listening and LingQing, I can easily move to fluency if I have enough exposure in real situations. And of course, the main thing is to enjoy the process.