*Private English lessons.
Seriously? My dictionary says, that a "private lesson" is the word I need in general. So why is "english private lesson" not the right word for a private lesson in english?
Because
private lesson is
not a word, but a two-word phrase—
private, an adjective, plus
lesson, a noun.
In
English lesson, meaning 'lessons about English',
English is functioning as a noun, not an adjective. (If
English is an adjective,
English lessons means 'lessons from England'.) Combinations of two nouns in English are usually treated like a single word in English grammar, even though they are often spelled as two words. This is the case for
English lesson: you can't put an adjective like
private between the two nouns
English and
lesson because
English lesson functions as a single word.
And then the people say, that german is a complicated language…
German and English are actually very similar in this regard! The difference is only that German almost always writes its noun-noun combinations as a single word, whereas English often writes them as two words even when they function as a single word.
I don't actually speak German, so I don't know if this is a good example, but: is there a difference between an
englische Lektion and an
Englischlektion? If so, that's the same thing as what I'm talking about for English.