There have been some surveys of German public opinion recently. The phrase in German here is "Der Islam gehört zu Deutschland". This is not an easy phrase to translate. It could be rendered in several different ways, each with slightly different connotations. You could translate it as "Islam forms part of Germany", "Islam is part of Germany", "Islam belongs to/in Germany". The statement that "Der Islam gehört zu Deutschland" was made a few years ago by now disgraced and out-of-office German President Christian Wulff. Merkel has also used the phrase since. But 72% of Germans reject the proposition.
A much higher proportion agree with the statement that "Germany is a country of immigration". Note there's an ambiguity in this (in the original German, not the translation). It could be interpreted as saying "Germany has become de facto a country of immigration", which is obviously true, or "Germany should be a country of immigration". 68% agree with this proposition; 28% reject it.
Another international comparison of self-declared patriotism shows that only 9% of Germans are very patriotic.