Complex sentence: In 1796 he went to Berlin, where he founded a humanitarian society, and was commissioned by the freemasons of that city to assist Fichte in reforming the statutes and ritual of their lodge.
Split into simpler sentences: In 1796 he went to Berlin, where he founded a humanitarian society. Fessler was commissioned by the freemasons to assist Fichte in reforming the statutes and ritual of their lodge.