As a tourist, you do not have to know the language, but there is one crucial reason why it would be so much better to visit Germany while you have some language skills: you will add so much more value to your trip.

You can travel through Germany very easily without speaking a word of German, especially in major cities like Berlin, Munich, Frankfurt, and Hamburg. English is a mandatory subject in German schools, and most people under the age of 50 speak it with high proficiency. In tourist hubs, restaurants, and hotels, the staff will almost certainly be bilingual. Public transportation machines and signs in major stations are also dual-language. However, if you venture into very rural parts of the former East Germany or small villages in the Bavarian forest, English proficiency may drop among the older generation. In these cases, a translation app or basic "politeness" German (like "Guten Tag" and "Danke") goes a long way. Germans are generally very practical and will go out of their way to help a "confused foreigner" using hand gestures and basic English if they see you are making a genuine effort.