Johan

@Questor and Simone: I somehow agree with you both, but I think you are reading more than what is written. This answer boils down to : "I think dressing for work is the norm and I think you should follow the norm." Why? What are the risks if not w/ German labour laws? Is it the norm in the particular sector (research) and culture (germany) OP works in? (from my experience, it isn't.) Can they hope to find a more accommodating company? Or should they try to negotiate on those expectations and contact their union if any? So much questions not addressed by this answer.

This answer is very old-school, why not also say that OP needs a good firm handshake and to dress for the job he wants and not the job he has? OP does not want to be "successful", whatever it may mean, he has his work and his life and is satisfied with both. Why not address the heart of the issue: OP is having a conflict and seems ready to push back on those expectations. What is the diplomatic way to do this and what are the risks?