Conversation so far:
What did Sven Hedin do in nazi germany?
Hedin's conservative and pro-German views eventually translated into sympathy for the Third Reich.
what was his influences?
Adolf Hitler had been an early admirer of Hedin, who was in turn impressed with Hitler's nationalism.
what did he do for hitler?
Hedin met Adolf Hitler and other leading National Socialists repeatedly and was in regular correspondence with them.

Question: what did they correspond about?
Self-contained rewrite: what did Sven Hedin, Hitler and other leading National Socialists correspond about?