Or unless you take a night train. Get in in the evening, sleep most of the way and wake up at your destination. That can actually save you time compared to a flight, or be a lot more comfortable than, e.g., getting up at 4 AM to take a flight to a meeting in the morning somewhere.
I was speaking more generally, sorry; there is currently no daily Paris-Berlin night train (and I guess the weekly Russian train is suspended). The most reasonable connection seems to be: Paris 19.04 (ICE 9557) 22.17 Mannheim 23.47 (Nightjet 470) 07.38 Berlin, with some time to drink a nightcap in Mannheim, but I can see how that won't work for everyone. You can also leave Paris at 17.55 and change more comfortably in Karlsruhe with maybe a late dinner. In the reverse direction you'll have an unpleasant change in the early morning though.
In daytime, there are a few options with only one change, but you'll sit in a train for 8 hours or so, which may not be your thing.
