I have a Kalkhoff Image 5.b Season (with coaster brake) which was in need of having its chain replaced. Having moved within the last year I have been using this bike as my main way of getting to work everyday since then. I am not an experienced bike mechanic but have decided I better get the hang of it myself as it is my only means of transportation besides public transport.
Anyways, I bought a new chain and tools to do the job. But I cannot figure out how to adjust the chain tension on the bike. The dropout appears vertical to me and I have been unable to locate anything in the manual regarding adjusting the chain tension. There are several screws on the bike frame itself - and I would suspect some of them might be related to this. I have tried loosening/tightening the ones that looked the most plausible to me - but so far without any productive results.
Closeup of the other side of the bolt on 2nd image: