Some aspects of the game can only be learned by actually playing. However you can minimize this necessity to play. When I first decided to play, I only studied the beginner section of Sensei's Library. After a few weeks doing that, I signed up to KGS and immediately got to 20k. A bit later I discovered 321go.org, did the course and the exercises there. This took me another two months and I got to 15k (ok, I also played a few games on KGS, maybe a dozen).
As Magicwand suggested earlier, you can improve very much by just studying professional games, this may be an option for you. However in another thread where I asked the question how much you can progress from studying professional games, it was said that you should be around 8k at least, so that you roughly understand why moves were made. One person made it from 8k to 1d, another from 1d to 5d. But I don't know how long it took them, how many games they studied and which games.
So there is still a gap from 15k to 8k that you would have to bridge somehow. Maybe teaching games are an option for you, e.g. from a fellow German, if you prefer discussing in your native language. I could help you to pass the 8k hurdle, if you like (after you have done 321go
Good luck.