Germany thought the wall coming down would give them more power and more prosperity but they badly miscalculated and it has economically weakened Germany to the extent that there are many west Germans who regret the wall coming down and the reunification of Germany. I can't remember who said it, but back in the thirties someone said that if Socialism could work anywhere, it would be Germany because the Germans had such a strong work ethic and discipline.
It seems to me that 2 or 3 generations under Communism is enough to breed away any trace of work ethic or discipline. Of course, West Germany went pretty damn socialist too and is weaker for it, but not quite as ruined as where full communism was entrenched.
The biggest problem with East Germany was that no investment had been made with the factories in the East and they were in such a terrible state companies who wanted their old factories back did not realise until they had them what a mess they had.
To bring them up to modern standards would have too much for too little return hence many were closed and then people were out of work and into the welfare system hence more drain on Germany.
In addition to that jobs that were available were low paid ones which some of the east Germans would probably have taken but were already taken by immigrant turks so all in all a total economic mess in what had previously been one of the strongest economies certainly in Europe if not worldwide.