Final answer:
The opening of East Germany's borders led to mass migration and the collapse of Communist governments. East Germany's biggest problem after opening its borders was its struggling economy and infrastructure.
Step-by-step explanation:
The opening of East Germany's borders had several important effects. One of the most significant effects was the mass migration of East Germans to West Germany and other non-Communist nations.
This migration put pressure on the East German government and ultimately led to the collapse of Communist governments in Central and Eastern Europe.
After opening its borders, East Germany's biggest problem was its struggling economy and infrastructure. The East German infrastructure was far behind that of the West, and significant investment was needed to update transportation systems and other areas necessary for industry and commerce. Unemployment was also a major issue, requiring retraining of the workforce.