Technically it’s the other way around - the ones German lost in comparison to Russian were the Instrumental and Prepositional (Locative).
This is from the original 8 (or 9) cases in their ancestor, Proto-Indo-European: Nominative, Accusative, Instrumental, Dative, Ablative, Genitive, Locative, Vocative, (Allative).
Russian has 6 cases. two more than german.
the added ones are instrumental and prepositional.
Technically it’s the other way around - the ones German lost in comparison to Russian were the Instrumental and Prepositional (Locative).
This is from the original 8 (or 9) cases in their ancestor, Proto-Indo-European: Nominative, Accusative, Instrumental, Dative, Ablative, Genitive, Locative, Vocative, (Allative).