What was the main idea of president reagan's speech reading plus?

If you are referring to the tear down this wall speech, then the idea was to tear down the Berlin wall, both literally as in connect the two parts of Germany again, and symbolically, to tear down the wall between the two ideologies and bring the countries together. Regan believed that Gorbachev and he should work together to bring the cold war to an end and open up to mutual cooperation, not just sit in their houses living in fear over who would throw the first nuke on each other. He believed that the Soviet Union should work together with the United States.

  
On June 12, 1987, U.S. President Ronald Reagan made one of his most famous speeches, in which he appealed to then Soviet Union General Secretary Mikhail Gorbachev to "tear down this wall." The "wall" refers, of course, to the Berlin Wall — the physical barrier between West and East Germany, as well as the symbolic barrier between two political ideologies: democracy and communism.  
You probably already know that, at the close of World War II, Germany and its dictator Adolf Hitler were defeated by the allied forces of the United States, France, Great Britain, and the Soviet Union. At the Potsdam Conference in 1945, it was agreed to divide Germany among the four occupying countries, in an effort to keep history from repeating itself — that is, a unified Germany rising to power again under the rule of a brutal dictator. Eventually, the territories occupied by the U.S., France, and Great Britain became the western bloc, or West Germany, while the eastern bloc became East Germany, which was widely considered to be a puppet state of the Soviet Union. In the years after the war, freedoms continued to erode in East Germany, and finally in 1961, the Berlin Wall was constructed, which not only completely closed the borders between the two Germanies, but also served as the most visible symbol of the Cold War.  In the 1980s, communism began its long and steady decline in the Soviet Union and Western Europe. President Reagan saw the opportunity to try to urge on that decline by visiting the Berlin Wall and giving this memorable speech, which not only called for the dismantling of the Wall, but also for the reunification of Germany. Just a couple of years later, the East German government fell, as did the Wall itself, and in 1990, the two Germanies were reunited under one democratic government. These events were perhaps the "last straw" for the Soviet Union, which was dissolved a year later.