countriesMarker: marker[] = [
      {
          lat: 51.673858,
          lng: 7.815982,
          label: 'A',
      },
      {
          lat: 51.373858,
          lng: 7.215982,
          label: 'B',
      },
      {
          lat: 51.723858,
          lng: 7.895982,
          label: 'C',
      }
  ]