Magath was appointed on Friday after Rene Meulensteen's brief spell in charge of the Cottagers was cut short and the German has 12 games to steer his rock-bottom side out of the Premier League drop-zone.
Fulham's players have already been put through their paces by Magath, who has a reputation as a tough taskmaster, and Riether is glad to link up again with the man he worked under at Wolfsburg.
When asked about training, he told Sky Sports News: "Very, very tough, yeah. A little bit different, but we know that we have to work hard.
"We are last in the table and I know how Felix Magath works. I had it three years in Germany. We have to work hard, but we will have success.
"He has to get to know all the players and the teams and all that is around the team.
"But in Germany, he never got relegated with all the teams and he knows how to handle difficult situations, so I hope he will handle our situation as well.
"I trained very hard for three years, but we were champions in Germany with Wolfsburg and he had a lot of success with Bayern Munich as well. I hope we will have success with Fulham."
Asked whether Magath can keep Fulham up, he replied: "Of course."
Swedish forward Muamer Tankovic believes Magath has already lifted the mood in Fulham's struggling squad.
"The new manager is here, so we're starting over again and hopefully we'll do something good. We'll stay in the Premier League," he said.
"Training has been very good. Everybody is very happy. He works very hard, he's a very good coach and hopefully we'll have success this season."