Complex sentence: Besides, he published praising essays about "Tannhäuser", "Lohengrin" and "Der fliegende Holländer" but did not share Wagner's ideas with regard to the "Kunstwerk der Zukunft".
Split into simpler sentences: Besides, he published praising essays about "Tannhäuser", "Lohengrin" and "Der fliegende Holländer". But he did not share Wagner's ideas with regard to the "Kunstwerk der Zukunft".