Beautiful 2-3 room apartment in Dortmund with a kitchen and good access to public transport

I obtained a PhD in Chemistry from Heidelberg University and I have now moved to Dortmund for my Postdoctoral research. I have been in Geramny long enough to understand the language almost fully but I am not able to speak German fluently yet. I am looking for an apartment with a minimum stay of 2 years but without a maximum limit. I have had some wondeful persons as landlords in the past while I lived in Heidelberg, and I look forward to building such a relationship here in Dortmund too. I am a very friendly and easy-going person who enjoys having conversations with new people.