Short answers, pulled from the story.
Ronald Reagan delivered his speech at the Brandenburg Gate on the 12th of June 1987. The event took place at two o'clock in the afternoon while East German police prevented citizens from coming close to the wall.
Peter Robinson drafted the text containing the phrase after traveling to West Germany to inspect venues. Anthony Dolan offered an alternative account claiming Reagan originated the line during an Oval Office meeting before Robinson's draft.
East Germany's communist rulers dismissed the speech as an absurd demonstration by a cold warrior. Politburo member Günter Schabowski recalled this reaction decades later and Soviet press agency TASS accused Reagan of giving an openly provocative war-mongering speech.
The president stood before the Brandenburg Gate in West Berlin on the 12th of June 1987. Two panes of bulletproof glass shielded him from East Berlin during the address while West German president Richard von Weizsäcker watched closely.
Ronald Reagan's speech followed John F. Kennedy's famous 1963 speech Ich bin ein Berliner which also took place at the Brandenburg Gate. Author James Mann placed the speech in context of previous Reagan overtures such as the Reykjavik summit of the previous year.