How well did Hitler succeed in taking over Europe?
The lack of a time frame here is a challenge. There was a point, at his zenith, where Hitler was fairly successful in bringing the Nazi influence to the European continent. For the most part, there was a distinct moment in time where Hitler accomplished his goal of ensuring that Europe was under Nazi control. Yet, it was not sustainable. Facing severe challenges from England to his West, Russia to his East, especially so when the Nazis cross through Poland, and American participation in the war, Hitler faced much in the way of being pushed back. Once the Allied Forces had committed to defeating him, Hitler's presence in Europe was retracted into Germany and then defeated, in general.
You do not specify when you are talking about, but at around the middle of 1941, and even into the winter of that year, Hitler had succeeded amazingly well in taking over Europe.
By the time winter set in that year, Hitler's forces controlled just about all of the continent of Europe. They had conquered all of Western Europe except for the neutral countries like Spain and Portugal. They had conquered essentially all of Eastern Europe, moving deep into Russia. So at that point, there was pretty much nowhere on the continent of Europe that was actually fighting against Hitler.
Hitler failed completely in his efforts to taking over by force in war, territories belonging to other countries. Hitler did achieve some spectacular victories in the World War II. Starting from September 1, 1939 Hitler invaded Poland, Denmark, Luxembourg, Sweden, Netherlands, Belgium, Norway, France by June 1940. The fighting also spread to Greece and Norther Africa after Italy joined hands with Germany in June 1940. In June 1941 he invaded USSR.
But slowly the successes of Germany were declining. By 1942 advances of Germany in Russia were stopped. Allied forces landed in Italy in 1943 and in France in 1944. In 1954 the Allied forces drove into German territory from the East and the West. By May 7, 1945, Germany was completely defeated and forced to surrender. Thus Hitler failed to achieve anything for Germany as a result of World War II.