+1 on the hydrometer readings being the same over 3 days (dont bother for at least a week and then again two days later to see if they are the same)
Also, you can use Beersmith or MashPro to see what your estimated final gravity should be so you know if you ended close. if it is supposed to be 1.15 and you end at 2.5 then you know there is an issue and not that it is done.
I was ignorant recently and decided not to do gravity measurements for a few beers and I regret every bit of it and if I did not with my last one i would have been screwed as it is supposed to end around 1.15 or somthing and it stopped fermenting at 1.30
I have never brewed a Dunkel, but many times people dont use secondaries so you could just leave it in the primart for the three weeks and call it a day. Less waste, yeast clean up after themselves, and you have less risk for infection (which with sanitary measures is low anyway)