Complex sentence: The minority in Danish Southern Schleswig, Germany has existed since 1920 and has ever since then been financially supported by the Danish state and has run Danish schools and clubs in the region until 1926 only in Flensburg and thereafter in the entire region.
Split into simpler sentences: The minority in Southern Schleswig has existed since 1920 and has ever since then been financially supported by the Danish state and has run Danish schools and clubs in the region. Up to 1926 only in Flensburg and thereafter in the entire region.