Staying at this hostel was excellent, except for a detail. When I arrived, I was assigned to bed 8. When I arrived to the assigned room, I found out that bed 8 was already occupied, so I returned to desk to report it and the hostess told me to pick any other bed. So I picked bed 4 and left some stuff on it. I went out for sightseeing and returned night late, finding out someone else was sleeping in my picked bed. Since it was late, I just picked bed 2 to sleep and take a rest. Then at morning I reported the issue and the host assigned me bed 2 and I didn't have any issue since then.
For everything else, it was perfect. Wifi in almost all areas, terrace to relax, kitchen and dining area. Also, it's very close to Köln Hbf.