Köln is a nice city which proves if you are comfortable in your own country you'd better live there than abroad.
is cozy, cute, gives you the impression of being very secure, something
in between a Dutch and a Swedish city, very tranquil, where you can lead a regular life.
you were born there, you are familiar with the local culture, with
lifelong friends and your family living nearby what can you demand more?
you are a tourist you can also enjoy a holiday in Köln: eating relatively
cheap, trying real kebab or some other specialties, having (many) 0.2 cheap beers
of good quality, enjoying the cool squares, the pubs where people of various ages go, checking if you come across someone who speaks a decent English (it can happen if you are lucky).
problem arises if you go live there without roots, it may become a kind
of rubber wall. Everything works properly, you can even get a decently
paid job, a good unemployment subsidy in case they don't keep you after 6
month probation, one of the best welfare systems in the world.
Still it would be very hard to penetrate that culture, to become part of that environment.
Life is hard everywhere, but sometimes it's harder where at first sight you would asses it as "the almost perfect place"