I was invited for an interview in a German university in Ruhr area, for a Junior Professorship position. In total three people (including me) were interviewed, so I guess it should not take so much for the committee to decide! Does any one have any idea how long it will take for them to conclude the recruiting process? I have an offer for a postdoc and need to let them know if I would take the offer for the postdoc. Thanks.
Christian Clason's comment is basically correct. The hiring process for W1 is the same as W2 and W3 and reports are collected after the interviews. So the time from interview to notification is not short. However, it don't need to be six month.
What usually happens after the interviews is that the committee solicites reports and the referees get about six to ten weeks for their reports. Then the committee meets again and forms its recommendation. This is the first point at which you may be told your suggested listing, but this is unofficial and at some places even against the rules. The next steps are that a number of committees have to approve the list (can be something between two and four) and only after the head of the university has approved the list, the first place may be informed officially. This whole process may well take six months, but it can be less, but do not expect less than six weeks between interviews and unofficial notification and not less then three months between interview and official offer.