Conversation so far:
What was Marc doing in France in 1923?
In 1923, Chagall left Moscow to return to France.
What was he looking to do once he returned?
On his way he stopped in Berlin to recover the many pictures he had left there on exhibit ten years earlier, before the war began.

Question: What kind of pictures he was into or did?
Self-contained rewrite: What kind of pictures was Marc into or did?