The 28-year-old Gashi from Bavaria told the Südkurier that he had traveled to Syria to “help and to look for answers.”
He explained that he was patrolling the Euphrates River in an area between Membis and Jarablus near the Turkish border.
“At moment I am guarding the Euphrates,” he wrote. “We are looking for smugglers who bring illegal goods here like cigarettes, alcohol or drugs, which are completely forbidden.”
He has not yet been involved in gun battles, he claimed, although he carries a weapon as part of his job.
“By the grace of God I have not yet had to use my weapon,” he said.
But he had seen an execution, he admitted.
“The deterrence effect is very big and there have been very few similar cases since."
"There are lots of Germans here," he added. "I only need to speak German and English, and a little bit of Arabic."
Successful, outgoing, friendly
Speaking to The Local, a former coach of Gashi's said that there were two sides to the champion fighter, the sportsman and the private person.
"I never saw the private side of him. As a sportsman he was very normal, but he never spoke about religion in the gym - that was taboo."
"As a champion boxer he was a model for children. But what he is doing now is no example to set."
But kick boxing has "nothing to do" with Gashi's turn to fundamentalism, the coach said. "He could have just as easily been a table tennis player or a footballer "
In Gashi's private life there also seems to be little to indicate he would have turned to jihadism, writes the Süddeutsche Zeitung (SZ).
He came to Germany at the age of six as a refugee from Albania. He grew up in Neumarkt where he found success as a sportsman and in the theatre.
His passion was kick-boxing and he moved to Singen in Baden-Württemberg, where he was trained into a european and world champion.
He later married and is the father of two young daughters.
One childhood friend described him to the SZ as a “prince who everyone on the street knew and greeted.”
“He was extremely approachable, happy and friendly.”
The friend said that during his life in Neumarkt Gashi showed no outward signs of religiosity.
"Someone must have planted these ideas in his head," said the friend.
Active on social media
Gashi still keeps up an active social media presence, slotting seamlessly into Isis' massive online propaganda effort.
His regularly updated Facebook page contains an almost surreal dialogue between Gashi, his critics and supporters, complete with memes, emojis and hashtags.
One user writes “Scum of the earth.. Shoot you and ur filthy ISIS POS, drop a Bomb on your head so u can die in hell.”
Another tells Gashi “don't let yourself be provoked by such people brother. Trust in Allah.”
Gashi responds to the controversy by writing “too many violent comments on my facebook page… need a banana with honey to relax.”
Underneath he has posted pictures of himself with a banana in one hand and a pot of honey in the other.
In another post titled ‘helping or fighting?' Gashi posts a picture of himself rowing a boat, smiling and looking relaxed.
“If you really know me, you would know that i don't do something stupid. But anyway....keep insulting me if it makes you happy,” he writes.
According to the German intelligence services the number of people going to fight for Isis has risen considerably since the start of the year.
Interior Minister Thomas de Maizière announced in March that an estimated 650 Germans have gone to fight for the Islamic fundamentalists.