Hello. Access to #20 when routing is still shown from Weitbrucher Weg (north of it). There is no path there, just two fences of #1. 
Of the three footpaths from Rathenower Strasse only the western one (to #20, not #21A) is closed with an electric gate, the other two (to 20 and to 19A) have a manual gate but are accessible. (Path to 18A is correct, completely open.)
Thanks for fixing that, several delivery drivers (like GLS) will be grateful.