What goals did Stalin pursue when he agreed to negotiate with Germany in the 1930s?

Stalin in 1939 needed to solve several problems:

Revision of the Riga Treaty with Poland from March 1921, along which the border passed 40 kilometers west of Minsk. As a result, the Third Reich attacked Poland, and the USSR announced a liberation campaign on September 17 and annexed a large territory in the west.
Conclusions of a non-aggression pact with Japan. In Tokyo, the pact of 23 August 1939 was considered a strange step on the part of Hitler, and soon they themselves concluded the same pact with the USSR and ceased operations on Khalkhin Gol.
The resumption of trade with Germany, they made good machines, the USSR needed them.