that looks like RD6800 to me at the back, 105 chainset etc so the groupset is a bitza. Also the hose routing to the rear caliper is so crap that I don't think you could fit a cable-operated caliper; if so, it is hydros only. Obviously everyone will want something different but I'd want to be able to fit 28s (at least) and mudguards.
Frame looks like welded aluminium to me.
The title of the photo is 'Kesselrun' so maybe Gradbach is not the only name under consideration.
cheers