If you plan to use a car here - don’t. Due to congestion, multiple simultaneous road construction projects, paid parking in an already big and still growing part of the city using public transport is now a better option.
The lion’s share of people engaged in service industries, retail etc don’t know English at all. Learning some Russian will probably help, although in many cases there’s an option to use an automated terminal instead of interacting with humans.
Vast distances. It’s absolutely normal here to spend two hours of your life on transit daily, and that’s if you’re rich enough to live in Moscow proper and not in one of the satellite cities.
Springs and falls (especially closer to winter) are very entertaining: precipitation and squishy mud everywhere.
Aside from that, I find Moscow to be an extremely comfortably city to live in - unless you want to hear about doing business here, and that’s a totally different story with its ups and (mostly) downs.