Russian is probably somewhere in between. How hard a language is to acquire depends a lot on what language or languages you already speak, but for native Englis

Russian is probably somewhere in between. How hard a language is to acquire depends a lot on what language or languages you already speak, but for native English speakers, Russian is considered difficult, but probably not "one of the most difficult." The Defense Language Institute, which provides instructions for native-English-speaking US military translators, classifies Russian as a category 3 language (of four categories), which makes it harder than French or Spanish (category 1), or German (category 2), and on the same level as Farsi or Hindi, but easier than the a reasonably-sized swath of category 4 languages that includes Mandarin, Japanese, and Arabic.