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 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.

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.

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.

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!

Berlin, Berlin – We're going to Berlin! On the excursion to the capital, Stimpel is primarily concerned about the safety of his charges, because Berlin is also the crime capital. Suddenly, Osman goes missing. While Sahra and Stimpel embark on a nighttime rescue mission into the Berlin nightscape, the students' arguments escalate at the party in the hotel.

Stimpel wants to expose the girls skipping gym class and develops a top-secret "period diary." But his entries lead him to a completely different suspicion: Kira might be pregnant! He knows he has to handle the matter with utmost discretion—and soon the whole school knows. Yunus, too, has to grapple with the possibility of pregnancy after his latest one-night stand and is completely overwhelmed.

It's supposed to be a simple, annual event: class photos. Stimpel is shocked by his students' obsession with beauty, but suddenly he himself is caught up in the pressure to improve. Between botched makeovers and teenage love chaos, Stimpel suddenly finds himself trapped in the beauty saga.

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 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.

Bestselling parenting guide author Schubert is coming to the school for a reading—and he brings chaos with him. Because he's Annika's father and therefore also Sahra's ex. She has some scores to settle with him, and Stimpel finds himself caught in the middle of a bitter custody battle.

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."

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?

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!

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.

Newly nominated for Teacher of the Year, Frank Stimpel has invited the press to film a segment about him and the school. What begins as a favorable profile quickly turns into a scandalous report that paints the entire school in the worst possible light. Swift action is needed.