If you are very keen on improving your karate then like any other skill or knowledge you need to practice in your own time as much as possible, if you can do at least half an hour to an hour a day with one day rest then you can improve faster. Most important thing for a new brown belt is to start relaxing more and get more fluid and less rigid,. This can happen with less tention in the limbs, shorter kime or focus. You only need kime or focus at the point of impact, the shorter your kime the faster and more powerful your technique! It doesn't happen overnight, it takes a while to get there, more you continously work on it the sooner you get there, having a good coach or guide is very helpful.