Unless you plan to move here and settle in a small town or rural area or you want to become an utter expert in german philosophy, literature, theatre etc. you don't need to learn German. In Berlin, München, Hamburg, FFM etc. you'd have no problem getting along using English only and the enormous amount of translated works, summaries and opinion pieces available for native english speakers in libraries and online should entirely suffice for building up a vast amount of philosophical and political expert knowledge.
Also keep in mind that the german language is officially used in Germany, Austria, Switzerland, northern Italy, Luxemburg, Liechtenstein, eastern Belgium and Namibia only while French and Spanish both have a lot more native speakers around the globe. Moreover, the French literature tradition is at least on par if not superior to ours, for a couple centuries pretty much every important european author used to publish in French additionally or exclusively.