Two surgeries later and fearful of being attacked again, the openly gay 52-year-old taxi driver -- who doesn't want to be identified because of concerns of another attack -- avoids public spaces and always takes pepper spray with him. He and his partner have also been forced to move neighborhoods in the northwest German city of Bremen following mounting costs as a result of being injured.
"I went outside and saw someone kicking my partner's head. I was trying to stop him and right at that moment, I got hit from the side," Karsten recalls about the attack. "I kind of lost consciousness and when I got up again, I thought my partner was dead. He was all covered in blood and he didn't move at all."
Police identified the attackers as two locally known Muslim extremists. They were never arrested and later fled to Syria. After demanding answers from local prosecutors and the mayor's office and not getting a response, Karsten turned to Germany's far right party, the Alternative for Germany (AfD).
"I don't like everything they say," Karsten says, "but this is too dangerous for gay people to live openly here, if we get attacked like that. We need a party that's talking openly about this."
The anti-immigration, anti-same-sex marriage party
Campaigning on a vociferously anti-immigration platform, the four-year-old AfD party now has seats in 13 of the country's 16 state parliaments. It has proposed a ban on mosque minarets and cutbacks on migration, from within the European Union and beyond, while its party manifesto says that "Islam does not belong in Germany."
Critics accuse the party of being a flimsy disguise for neo-Nazi sentiment, and cite one candidate who allegedly sent a photo of Hitler to some AfD supporters with the text: "Adolf please get in touch! Germany needs you! The German people!"
Germans vote in national elections this month
, and the AfD is contesting them for the first time. The party is polling around 9% in recent days, which could put it in contention for third or fourth place, well behind Chancellor Angela Merkel's center-right Christian Democrats and the center-left Social Democrats, who have ruled out entering into a coalition with the AfD.
In some ways, the AfD is an unlikely place for lesbian, gay, bisexual and transgender (LGBT) voters. The party has threatened to sue the government for allowing the recent vote to legalize same-sex marriage, and the AfD manifesto advocates the "traditional family as a guiding principle."
Yet one of the AfD's top candidates, Alice Weidel, is an openly gay woman raising children with her partner. Weidel, an economist, was brought in as the softer, moderating face of the party, but her campaign speeches show she can deliver an angry rant on immigration as well as her AfD peers.
"Merkel's refugee policy will destroy our welfare state of the Federal Republic of Germany!" she said in a recent campaign post. "We, as AfD, will make sure that this comes to an end. Because open borders do not work with a sustainable social state."
People like Karsten and Sven aren't alone in supporting the party. There is even a German term for gay support of the far right: "homonationalism." A 2016 survey from "MEN," a monthly magazine for gay men, showed that 17% of respondents openly supported the AfD, higher than the national average.
"A party like the AfD gives people from minorities an offer of social identity," says Beate Kupper, a social psychologist at Hochschule Niederrhein University in North Rhine-Westphalia who studies the far right in Germany. "If you identify strongly with a group and you have an 'out-group' that you can position yourself against, that is a good feeling for your personal belonging."
Kupper singles out Weidel's campaign speeches as a particular example of this. "If you look at Alice Weidel, she's an economist, so her expertise is on the economy. [But] she is not speaking that much about the economy. Her topic is very much devaluation and hatred towards Muslims. Muslims are now the identified out-group."
Mirko Welsch was also once an AfD supporter, initially drawn to the party by its resistance to the euro currency. He was even an elected AfD official in his district council of Saarbrucken, a rare feat for a gay member of the party.
"I was convinced that the AfD would grow as a party into a well-respected opposition to the Christian Democrats," he says. "I believed in what it originally stood for."
But he became increasingly uncomfortable as party leaders ratcheted up the anti-immigration rhetoric. He resigned in March, after one AfD leader called for a "180-degree turn" in the way Germany deals with the Second World War, particularly "national guilt" over its Nazi history.
"The AFD has developed in a way that we are seeing incitement against different groups of minorities," Welsch says. "The party has just moved too many inches to the right."
Welsch believes that LGBT support for the AfD is actually dropping, despite Alice Wiedel's prominence within the party.
"You will see that many more AfD voters in the LGBT community won't vote for the party in the future. There is just too much turmoil going on," Welsch says, adding that his former party "has become a farce."
An untapped source of votes?
Welsch points out that he was once one of the 130 or so openly gay AfD members. That number now stands at 20, says Alex Tassis, the man who is now responsible for the AfD's gay outreach.
Tassis heads up Alternative Homosexuals, the AfD group that reaches out to the LGBT community. A gay immigrant from Greece, Tassis says he strongly believes that "Islamization" is a threat to Germany and Europe and that the AfD will soon become the most popular party among gay men. There's no contradiction in the party's stance against gay marriage, he says. And it's clear he views the LGBT community as an overlooked source of votes this election.
"Gays, lesbians and also older migrant groups in Germany -- like myself who came to Germany a long time ago -- are just as important to Germany as any other human being who lives here," he says.
"The LGBT and older migrant groups have concerns that other parties simply don't understand and don't get. I represent those groups and want to give those groups a voice. That's what I am here for. "
Tassis was the one who answered Karsten's email for help after he and his partner were attacked. Within three hours of reading it, Tassis met the couple in a downtown Bremen cafe and connected them with a lawyer, encouraging them to sue the local prosecutor, something the pair are looking into.
"Cases like Karsten's or similar cases have unfortunately happened in Bremen amongst citizens before," Tassis says. "This case was particularly dramatic. Every citizen has a right to be heard, every citizen needs an ear and this is what I did In Karsten's case."
That swift response turned Karsten from someone who used to vote for the left-wing Green Party into an AfD supporter.
"It has nothing to do with being a Nazi or being totally right. I'm not against every foreigner. And I'm not against every Muslim. But I'm against the criminals," Karsten explains. "This was the only way we could get some help. Because the other parties didn't care."