> It is not that different from German in this matter.

I've met several Germans who spoke Russian fluently, none of them has really mastered the instrumental case, not even a friend of mine who worked at the German embassy in Moscow. Although you might say it's a minor grammar difference, this particular grammar case seems hard to grasp for people who are not accustomed to it through their native language.

Also, from my personal experience, quite a few Germans who learnt Russian had a real struggle understanding the concept of perfective/imperfective aspect.

German inflection is pretty minimalistic. There are just four cases, and it's mostly the article that is being changed with only occasional and predictable changes to the noun itself. Meanwhile in Russian there are six cases and no article, so it's the word itself that has to change. Also there are three different declensions not counting exceptions.

Gender in Russian is much easier than in German though - most of the time you can tell it by the word itself

What's difficult really depends on the languages you already know.

In addition to noun inflection, verb aspect, pronunciation stress, and punctuation trouble many native English speakers. That's in addition to all the simple irregularities, like irregular nouns and verbs.

Stress even troubles native speakers. When I lived there, I saw slideshow "where 's the stress?" quizzes used to fill time on screens in taxi buses, waiting rooms, and the like.

>It is not that different from German in this matter.

Russian inflection changes the stress. In German it's fixed. Inflectional forms are much more varied in Russian. Colloquial German is much more analytical (past tense is almost always "ich habe" + participle). German has devolved to basically 3 cases at this point (with genitive dying out), compared to Russian's 6. But conceptually, they're very similar indeed.

If you just want to be understood, Russian is not very hard. I think it's true for any language. To master it, however...

The only difficult part of Russian is writing it. Most native Russian speakers, myself included, can't write properly even after completing 11 years of Russian language in school. Hundreds of rules nobody remembers.

> Russian grammar is inflectional, yes, but that's about the only difficult part of the language.

That's saying that getting to the lunar orbit is the only difficult part in landing on the Moon. The whole complexity of inflectional languages is in the inflections. It's also why Slavic (or Turkic) languages form such a large continuum of mutually almost-intelligible languages.

Compared to inflections, everything else in Russian is simple. The word formation using prefixes and suffixes is weird, but it's not like English is a stranger to this (e.g. "make out", what does it mean?). The writing system is phonetic with just a handful of rules for reading (writing is a different matter).