Since parliamentary democracy was restored in Germany after World War Two, several right-wing parties have sought to get the required 5% of the popular vote to be represented in parliament. They all failed until 2017. In that election a new right-wing party, Alternatives for Deutschland (AfD), won 13% of the vote, making them the third most powerful party, ahead of the Greens, the Lefts, and the Liberals. They also won many seats in the individual state parliaments and one seat in the European Parliament.
Exit polls showed, though, that most people who voted for them weren't convinced by their overall program but only by one aspect of it: their strong opposition to the government's permissive refugee policy.
Germany has taken in over two million refugees from the Mideast wars, far more than any other country. The equivalent for the US population would be eight million refugees, double the number of people in Los Angeles.
This has created an enormous financial and cultural strain in a country that historically has had little immigration. It comes at a time when poverty is increasing and social services are being reduced. The once-generous welfare state is being dismantled. This financial squeeze is worsening now because of expenses for the refugees. The two million newcomers receive enough money to live on plus free healthcare, education, and access to special programs. Some cheat on this, registering in several places under different names and getting multiple benefits. Many Germans resent paying for all this with high taxes while their own standard of living is declining.
The clash of cultures has created other problems. Two-thirds of the refugees are young men, some of them convinced God has ordained males to dominate females. In their view, women who aren't submissive need to be punished. Since being male is the only power many of them have, they feel threatened by women in positions of power, and they sometimes react with hostility. Over a thousand women have been physically attacked -- some murdered and raped and many aggressively grabbed on the breasts as a way of showing dominance. Tens of thousands of women have been abused -- insulted, harassed, spat on. Some examples: https://en.wikipedia.org/wiki/New_Year%27s_Eve_sexual_assaults_in_Germany
German foreign policy is also part of the problem. Many refugees are aware that Germany, as a member of NATO, supports these wars that have forced them to flee their homes. They're not fooled by the rhetoric of "humanitarian intervention." They know NATO's motives are imperialistic: to install governments agreeable to Western control of their resources and markets. Although they are now safe, their relatives and friends are still being killed with weapons made in Germany and oppressed by soldiers and police trained and financed by Germany. Rather than a grateful attitude, some have come with a resentful one. A few ISIS and al-Qaeda members, determined to drive all forms of Western imperialism from their lands, have come to murder and maim. For instance: https://en.wikipedia.org/wiki/2016_Berlin_attack
Crime has increased, especially violent crimes such as knife attacks. Police and others have been killed and wounded by refugees.
Many Germans are incensed by this behavior.