German economic performance brightened somewhat in the first months of the year, according to the country’s central bank. “Real gross domestic product (GDP) is likely to have increased slightly in the first quarter,” according to the Bundesbank’s monthly report published on Thursday. Previously, experts had forecast a slight decline in economic output at the beginning of the year. However, they said, it is not yet clear whether an apparent increase in economic output would continue in the second quarter. “Overall, there is still no sign of a sustained improvement in the German economy,” the Bu…