Germany’s economy minister on Saturday suggested tightening the rules on foreign investment, following concern over Chinese influence on European firms. Last month, it emerged that Chinese billionaire Li Shufu had quietly bought a near-10-percent stake worth around €7.2 billion ($8.9 billion) in German car giant Daimler — making him the group’s largest shareholder. “We must always adapt our law on the external economy according to new developments, including the threshold at which (the government) can become involved,” Economy Minister Brigitte Zypries told the weekly Der Spiegel. Currently, Berlin can scrutinize a transaction and possibly prevent it, if the foreign investor...