It's clearly a bit of a desert, judging from the lack of trip reports.
I think that's just due to the fact that most of the traffic is in German, and/or on German sites. If you're staying a whole year, it might be worth considering to set up an account on ornitho.de (it's free), the site is available in English too. Bear in mind that some vulnerable species on ornitho are automatically "protected" and will never show up in your searches. But those are mostly eagles and grouse and they don't occur in your area anyway.
There's also
this site, which is operated by the people who released the "Vögel beobachten in Deutschland" book series, consisting of three very interesting volumes covering the
NW, NE and South, respectively. Might not be available in English, but worth checking out anyway (they should also be present in university libraries, if you have access to one).
I will be about 50 miles east od Dortmund, so a long way from Brandenburg's waters and cranes
I'm guessing that's not far from Paderborn. One of our BF moderators (Andy Hurley I believe) is based there, maybe he can help with interesting sites in the region.
There are some "easy" continental target species for British birders that you should be able to see almost anywhere, i.e. Short-toed Treecreeper and Black Redstart. White Stork and Black Kite are not terribly difficult either, they should occur in the valleys next to rivers or other water bodies. Golden Oriole might be a bit trickier, I don't know much about its status in the region.
The Kellerwald-Edersee National Park in Hessen is also not too far away from that approximate area, might be worth checking out - it should have most of the native woodpeckers (i.e. Black, Green, Grey-headed, Greater/Middle/Lesser Spotted WP) as well as various owls (Eagle Owl, Tengmalm's, Tawny, and Pygmy Owl), Goshawk, Black Stork, Pine Marten, Wildcat, and maybe even the occasional Lynx or Wolf. Obviously some of these are very difficult to see, but they do occur in Central Germany.
The Rieselfelder Münster seem to be a popular destination with birdwatchers looking for wetland birds and migrant waders, should be a good start if you want to find a large number of species.