> I had my experience with bootstrapping a self founded UG (Unternehmergesellschaft), and the process was long (about 8 weeks)

It would have been significantly quicker if you used a well-connected law firm.

I know a number of friends of friends in Germany who have all visited the lawyer, the notary and the bank all in the course of one morning. The whole experience was orchestrated by the lawyer because they knew the notary and the bank manager. In some cases the lawyer even drove them around between locations. ;)

The Steuerberater then took care of the Finanzamt.

Of course this entails extra professional fees. But the point is that there are many examples out there showing it can be done in less than 8 weeks.