I used to live in Bremen and many many years ago I worked in that same pub! At the time I was there it was the best pub in town but I am not so sure nowadays. They also own a pub called Paddy's Pit which is by the Bahnhof.
But if you want the best Guinness in Bremen then go the
Irish Pub Schnoor I honestly only had nicer in Dublin. Also I think it is a pub that really does reflect an actual pub and not like any of the Irish pubs in Frankfurt.
I always found plenty of people to chat to in all those pubs