This post is specially covering the four-episode Augsburger Puppenkiste collection from 1977 and not the film remake of 2018.
This film is recommended for ages 3+ and does lean young. That being said, the language used is very clear and some conversations show grammar well (for example, discussing a package in various cases, with and without adjectives). Or in the second episode, there is a musical number that is paused to define a word, which is then corrected and explained that if it were used correctly, it wouldn’t rhyme. This song is repeated, along with the correction and explanation, in the beginning of episode 3. There are short scenes with dialect (Bayrisch and Hessisch) that use the local news music, which may be an interesting for some students.
Episode 3 also has some STEM education, explaining Fata Morgana with comprehensible language. The character that appears immediately thereafter explains perspective with a social-emotional connection.
Unfortunately there is some racism involved in the language as well. (A baby was in the package, when the woman opens it, she says “Schwarz ist es zwar, aber…”) The fact that this child is Black is important to the Jim Knopf series, but the modern remakes that I have seen to date have framed it in such a way to remove the racist undertones of the story. In the second episode, Jim and Lukas are in “China” and many of the characters are caricatures of the culture, which again continues the racist undertones of the series. The final episode includes stereotypes regarding schooling and adult attention. This same character talks about having bought Jim when he was a baby.