No, you cannot conduct business in other EU countries with an Germany Business Visa, you must apply for the business visa of that specific EU country. The Germany Business Visa provides authorization specifically for business operations within German territory. The Schengen Area includes Germany and many EU countries which allow free movement but the Germany Business Visa does not provide authorization to conduct business across other EU nations.
The nature of your business visit will determine whether you need to apply for a Schengen Business Visa or acquire extra permissions to visit other Schengen countries. Always check the specific visa requirements for each country.