Ok - ich muss sagen, ich kannte den nicht bislang - aber wenn er seit 10 (oder gar 20+) Jahren Resident DJ ist im Berghain, kann er nicht so schlecht sein, bin ja sehr selten dort in Berlin unterwegs noch - bin ja eher der Frankfurt Techno Typ - hört mal rein - ist ganz ok! Und sorry 
Marcel Dettmann - from former GDR (aka former Germany East) to Berlin
Did not came across him to be honest - stumbled over a video where he talked about his life history as DJ and that he was proud / happy to get the opportunity as stranger to play in Berghain - Berghain is one of the most exclusive Techno clubs in Germany (Berlin) - I thought the real exlusive ones been only in Frankfurt - however Berghain still exists and Marcel still plays a crucial role there. Feel free to listen to his interview (in German only):
Give him a chance
He plays the usual known locations (Boilerroom) and also events around Europe at least. His Ibiza performance striked me - was a good one:
Marcel seems indeed an OG of Berghain - playing and producing Techno since the 90ies (ok I was earlier). His main job starting point was 1999 as he started in a club called "Ostgut" - which then was renamed (or taken over) to / from the famous BERGHAIN.
Seems his own production been good but financually not the best ones - his label was closed in 2019 - however he is touring and is a good DJ for any party around the world.
Thought? Who knows him from my Berlin friends?
My favourite mix I came across yet is that one with Helenea Hauff - however stills struggle to define his main style - sure 
