old_contents: export default function formatNumber(number) {
  
    return new Number(number).toLocaleString("de", {
      maximumFractionDigits: 1,
      minimumFractionDigits: 0
    });
  }
  
new_contents: export default function formatNumber(number) {
    const locale = window.navigator.language || 'de';
    return Number(number).toLocaleString(locale, {
      maximumFractionDigits: 1,
      minimumFractionDigits: 0
    });
  }
  
subject: use window.navigator.language to format numbers