I have flown in France, where the government made it very easy to understand the rules. They issued a flier in English/French and there's a detailed map of altitude restrictions.

Where can I get similarly reliable up-to-date information for Germany, preferably in English?

There are several websites and forum posts out there discussing this, but none of the information I could find in English seems to come from official sources.  There is a mobile app called Airmap, which has a rather detailed map, and can also provide advisories.  Does anyone here know if it is reliable?  Where does their data come from?  
They also have maps for France, but it is clear that they are not reliable—they don't match the government-issued map (and neither do the rules they list). Theor maps for Germany are much more detailed, though.

I am sure that with enough effort I could google up the actual laws, but reading German legal texts is going to stay beyond my abilities for the foreseeable future.

(A note to those who just use the DJI map: in France it doesn't even come close to the actual restrictions.)

I have flown in France, where the government made it very easy to understand the rules. They issued a flier in English/French and there's a detailed map of altitude restrictions.

Where can I get similarly reliable up-to-date information for Germany, preferably in English?

There are several websites and forum posts out there discussing this, but none of the information I could find in English seems to come from official sources.  There is a mobile app called Airmap, which has a rather detailed map, and can also provide advisories.  Does anyone here know if it is reliable?  Where does their data come from?  
They also have maps for France, but it is clear that they are not reliable—they don't match the government-issued map (and neither do the rules they list). Theor maps for Germany are much more detailed, though.

I am sure that with enough effort I could google up the actual laws, but reading German legal texts is going to stay beyond my abilities for the foreseeable future.

(A note to those who just use the DJI map: in France it doesn't even come close to the actual restrictions.)