The formation and construction of the wall began on august 13, 1961, which divided west and east berlin by barbed wire and cinder blocks. this wall composition would soon be replaced by 15 foot high concrete walls topped with barbed wire and guarded by watchtowers, gun emplacements and mines.
what problematic events led east germany to erect the berlin wall?

The wall was built to avoid people flee from the Eastside (the soviet side), however, the most important reason was to isolate East Berim, supported by the Soviet Union, of the West Side, supported by the United States.

Explanation:

Berlin Wall was the might symbol of the Cold War. After World War II, the winners divided Germany, which lost the conflict, in four political zones, each one controlled by the victorious countries (France, United States, Great Britain, and the Soviet Union). In Berlin, the capital, however, two divisions highlighted: the West, controlled by the Americans, representing capitalism (Western Germany); and the East, supported by the soviets, representing socialism/communism (Eastern Germany). Many people were separated from their families by an imaginary border, but they were always trying to flee from one side to another. This motivated the Soviet Union leader at that time, Nikita Kruschev, to authorize the building of a concrete wall, separating the sides, to avoid more flees. But Berlin Wall didn't avoid people to continue to flee, and more of them tried to so during the time the Wall was there.