Complex sentence: Claus Stolz studied Fine Arts at the Freie Kunstakademie Mannheim and for more than twenty years has been working with this technique he calls "heliography"-sun drawing or sun writing.
Split into simpler sentences: Claus Stolz studied Fine Arts at the Freie Kunstakademie Mannheim. Stolz has been working for about twenty years with this technique, which he calls "heliography"-sun drawing or sun writing.