The new dream couple in the teachers' lounge, Frank Stimpel (Phil Laude) and Lisa-Britt (Sina Tkotsch), want to share their happiness: they offer a couples' dance class. But the class boycotts Stimpel's dance class, and Vice Principal Aminata Müller (Dela Dabulamanzi) supports his idea for a school ball. Yunus (Zejhun Demirov) and Sahra (Pegah Ferydoni) would prefer to boycott Lisa-Britt. But when the new, beautiful exchange student signs up for the class, even Osman (Mido Kotaini) and everyone else suddenly join in.

Stimpel, of all people, wants to educate his class. Everyone except him realizes that he has more to learn about sex than the students. Lisa-Britt (Sina Tkotsch) has evicted Yunus (Zejhun Demirov) from the apartment, leaving Stimpel (Phil Laude) all to herself. Osman (Mido Kotaini) is on the fast track to losing Kira (Derya Dilber). He wants to go viral with his first rap video and become a big star—with or without Kira.

Trip (Vincent Hahnen) tells of supernatural occurrences in the school basement. Dilara (Jansel Dogan) is convinced that her dead grandmother protects her and the class from the ghost with a magical eye. Stimpel (Phil Laude) thinks this is nonsense. He wants to prove that hauntings don't exist. But physics doesn't always provide the best explanation. Especially when emotions and Sahra (Pegah Ferydoni) are involved.

Stimpel wants to curb the aggression among the students. He makes several attempts until it becomes clear who the real problem is: the passive-aggressive Alman teacher himself!

Stimpel (Phil Laude) doesn't think much of influencer or rapper as a career goal and tries to inspire his class's ambition. He absolutely wants all of his students to graduate, even though Vice Principal Aminata Müller (Dela Dabulamanzi) just shakes her head at the idea. Stimpel invites fund manager Rolf (Edin Hasanovic) to be a motivator and job role model. He arrives in a fancy sports car and doesn't really behave like a suitable role model. It's a good thing that at least the career counseling AI is showing heartfelt concern.

Stimpel's big day is approaching: the teacher's exam! His class's drug problem comes at a very unfortunate time. To demonstrate the potential consequences to the young people, he conducts a self-test with fatal consequences.

The new shared apartment situation causes conflict: Lisa-Britt (Sina Tkotsch) is doing everything she can to get Yunus (Zejhun Demirov) out of the apartment. At school, Stimpel's (Phil Laude) headphones have gone missing. He suspects Kira (Derya Dilber), sowing distrust in the class that spreads rapidly. When it becomes clear that his suspicions may not be true, the German tries to discreetly backtrack, making everything even worse. Fortunately, Kira and the others manage to make a fresh start. After all, who wants to be like Stimpel?

The big prom is coming up, and teacher Stimpel (Phil Laude) also has big plans: He wants to propose to his girlfriend Lisa-Britt (Sina Tkotsch) – at the school prom in front of the entire school, of course. But is Lisa-Britt really the right one, or should he just say "yes" to his new school, with all the consequences? Stimpel has to listen to his feelings, but that's never worked out well.

Despite German customs, a new teacher captivates everyone with his open pedagogy and relaxed manner, causing Stimpel to doubt himself. When the new teacher then starts flirting with his colleague Sahra, Frank realizes: There can only be one German!

Stimpel, Sahra, and the entire class are going on a school trip to the forest – except for Stimpel, everyone finds it completely boring. Alman wants to change that and provides a little thrill. But the forest has its own rules.

To increase his chances of becoming a civil servant, Stimpel establishes a robotics company. But instead of action, the German prefers theory. His colleague Yunus counters this and establishes a combat robot company, which challenges Stimpel to a major showdown.

Stimpel becomes a guidance counselor and wants to prove himself in his new role to his boss, Aminata. Just when his student Leyla is in an emergency situation, the task becomes overwhelming.

Lisa-Britt (Sina Tkotsch) is lacking fire in her relationship, and Frank Stimpel (Phil Laude) isn't getting it. He spontaneously passes off a surprisingly emotional love letter from Robert (Tim Alberti) as his own, temporarily maneuvering his troubled relationship with Lisa-Britt back to cloud nine. Student Robert wins the class "passionate expression" by a clear margin. This puts him even better than Trip, who, in a moment of weakness, decides to take a tutor in masculinity from Hausklaus (Milton Welsh), of all people.

The class is so poorly prepared for the final exam that, according to Osman (Mido Kotaini), they have only one chance to pass: they must steal the sample answers from the principal's safe. Unfortunately, he hasn't reckoned with teacher Stimpel (Phil Laude), who does everything in his power to prevent the theft. A bet turns into an epic battle for the ominous envelope. Is Sarah (Pegah Ferydoni) really teaming up with the class against Frank?

Stimpel learns about an online ranking that rates the school's teachers based on their coolness. To earn the class's respect, he desperately tries to loosen up. To do so, the German has to step out of his comfort zone and resort to unusual means.

To raise money for the class trip, Stimpel initiates a school flea market—a hands-on way to learn economics. The fierce competition between him and Sahra, and the battle of supply and demand, leads to a "nasty situation."

Frank Stimpel has to prove himself at his new school. In his first week, he loses the class's respect, and the police show up. Principal Aminata would love to kick him out again, but she needs the German teacher.

Stimpel's attempts to improve security at the school fail due to class resistance. The Stimpel Security organization, or StiSi for short, he founded, aims to change this by any means necessary. But the German's plans begin to divide the entire school.