In Germany, tourists can normally get by with English without any problems. Even some jobs in international corporations do not require you to speak any German. However, if you are setting up your own business, a sound knowledge of German is very important. Even as you prepare your business, you will find that many official documents are available in German only. Similarly, your customers and business partners will expect to be able to contact you in the local language.
If your German is not yet good enough, you should make sure to take a language course before you set up your business. Some advanced courses have a special focus on the business world. If you know the most important German terms, this will help you particularly in the startup phase. In the beginning, you may still find that it is difficult to understand contracts and other formal texts straightaway. For this reason, it may be helpful to bring along a German-speaking friend or acquaintance to important meetings.
BMWi Overview no. 58: Where can I find a suitable German course?
Recognition in Germany